Systems and methods for determining an orthodontic treatment

ABSTRACT

Methods and systems for determining orthodontic treatment based on 3D digital model of subject&#39;s teeth. The method includes determining, for a given trajectory segment of the orthodontic treatment of a given tooth in which the given tooth is moved from a start position to an end position, whether the force required to move the given tooth from the start position to the end position causes an induced stress associated with at least one other of the plurality of subject&#39;s teeth. In response to the induced stress being outside of a predetermined threshold level, determining a counter force to be applied to the at least one other of the plurality of subject&#39;s teeth. The orthodontic treatment can be thus determined as including the force to be applied to the given tooth and the determined counter force to be applied to the at least one other of the plurality if subject&#39;s teeth.

CROSS-REFERENCE

The present application is a Continuation of U.S. patent applicationSer. No. 17/338,143 filed on Jun. 3, 2021, the content of which isincorporated herein by reference in its entirety.

FIELD

The present technology relates to systems and methods for determining anorthodontic treatment for a patient.

BACKGROUND

Planning an orthodontic treatment for a patient may include determininga desired position of one or more teeth of a subject to obtain a desiredconfiguration of the teeth in an arch form of the subject. The plannedorthodontic treatment may include determining a trajectory of movementof one or more given teeth of the arch form of the subject to a targetposition in one or more treatment steps. The so determined orthodontictreatment may then be implemented by applying one or more orthodonticdevices to the patient's teeth to exert an external force, over the oneor more treatments, to the one or more given teeth to cause eachrespective tooth to move along a given determined tooth trajectorytowards the target position.

However, it is important that the determined orthodontic treatment takesinto account safety of the orthodontic treatment in terms of avoiding orminimizing pain and/or damage to the teeth or other tissues of thepatient. A contrasting requirement is that the orthodontic treatment isefficient and minimizes an overall duration of the orthodontictreatment.

Certain prior art approaches have been proposed regarding the generationof teeth trajectories for the given tooth.

U.S. Pat. No. 9,161,823-B2 issued on Oct. 20, 2015, assigned to AlignTechnology Inc., and entitled “Orthodontic systems and methods includingparametric attachments” discloses orthodontic systems and relatedmethods for designing and providing improved or more effective toothmoving systems for eliciting a desired tooth movement and/orrepositioning teeth into a desired arrangement. The methods andorthodontic systems include tooth attachments having improved oroptimized parameters selected or modified for more optimal and/oreffective application of forces for a desired/selected orthodonticmovement. Attachments can be customized to a particular patient, aparticular movement, and/or a sub-group or sub-set of patients, andconfigured to engage an orthodontic tooth positioning appliance worn bya patient, where engagement between the attachment and orthodonticappliance results in application of a repositioning force orseries/system of forces to the tooth having the attachment and willgenerally elicit a tooth movement.

U.S. Pat. No. 6,739,870-B2 issued on May 25, 2004, assigned to 3MInnovative Properties Co., and entitled “Use of finite element analysisfor orthodontic mechanics and appliance selection” discloses determiningan effective orthodontic treatment by storing an original position modelof a patient's teeth. The patient's teeth are then displayed accordingto the original position model, and appliances are selected according toa proposed orthodontic treatment. A final position model of thepatient's teeth is also stored, and the selected appliances aredisplayed based upon the final position model. A finite element analysisis performed based on the proposed orthodontic treatment and on amovement of the patient's teeth from the final position to the originalposition in order to determine stresses, strains, forces, and/or momentson the appliances and on the patient's teeth and bone. If the stresses,strains, forces, and/or moments are not optimized, a new orthodontictreatment is proposed and the process is repeated.

SUMMARY

It is an object of the present technology to ameliorate at least some ofthe inconveniences present in the prior art.

The developers of the present technology have devised methods andsystems for determining an orthodontic treatment which takes intoaccount both efficiency requirements for minimizing the overall durationof the orthodontic treatment of the subject; and safety requirementsaimed at preventing damage to the subject's teeth and other anatomicalstructures.

Furthermore, the methods and systems devised by the developers canreduce a required resource from a computer system implementing saidmethods and systems. This means that in certain embodiments even complexcases requiring many iterations can be performed.

More specifically, the developers have appreciated that the toothtrajectory may be represented by a plurality of treatment segments,wherein a given treatment segment corresponds to a treatment step havinga predetermined treatment interval in which a predetermined force(referred to herein as “valid force”) is applied to the given tooth tocause displacement of the given tooth.

In certain instances, the valid force applied to the given tooth mayinduce a movement in other teeth of the subject. Such movement may beundesired and/or unplanned for and may necessitate additional treatmentsegments to correct the movement of the other teeth, thus prolonging theoverall treatment.

Thus, certain non-limiting embodiments of the present technology aredirected to determining if there is any induced movement in other teethof the subject based on the force applied to the given tooth. Theorthodontic treatment may thus take into account a counter force to beapplied to the other teeth to avoid or minimize their movement, or todirect a direction of their movement.

Thus, certain other non-limiting embodiments of the present technologyare directed to determining the valid force based on an optimization ofpreliminary applied forces and preliminary trajectory segments whichtake into account induced stresses associated with other teeth of thepatient (such as in periodontal ligaments (PDLs) thereof) andundesirable effects of these induced stresses. Undesirable effects ofthe induced stresses on the other teeth may include induced movement ofthe other teeth or damage to the PDLs of the other teeth, as well asdamage to the given tooth or the other teeth. In this respect,developers have proposed utilizing stress thresholds associated witheach teeth, such as a minimum stress threshold in the PDL below which atooth will not move, and an maximum stress threshold above which therewill be permanent or at least long lasting damage to the PDLs.

The so determined valid force can thus be used to determine a validatedtreatment segment as part of the orthodontic treatment, according tocertain non-limiting embodiments of the present technology. In certainembodiments, the valid force is a modulated preliminary applied force tominimize or avoid the undesirable effects. In certain embodiments, thevalid force is the same as the preliminary applied force but thepreliminary treatment segment is modulated in that a counter force isapplied to the other teeth while the valid force is being applied to thegiven tooth to minimize or avoid movement of the other teeth.

Accordingly, certain embodiments of the present technology are directedto manufacturing orthodontic appliances based on the validated treatmentsegment.

In certain embodiments, the validated treatment segment may ensure amaximum possible displacement of the given tooth whilst minimizing orpreventing undesirable effects from induced stresses such as damage tothe given tooth and other teeth, and undesired movement of the otherteeth. By so doing, embodiments of the methods and systems describedherein, may safely minimize a number of treatment segments, therebyreducing the overall duration of the orthodontic treatment. This maytranslate to a fewer number of associated orthodontic appliances to beapplied to the subject's teeth in the course of the so plannedorthodontic treatment. In certain embodiments, by avoiding or minimizingundesired movement of the other teeth during movement of the giventooth, a more effective and efficient orthodontic treatment may beattained.

More specifically, there is provided a method for determining anorthodontic treatment for a tooth of a subject, the method beingexecutable by a processor of an electronic device, the methodcomprising: acquiring a 3D digital model of an arch form of the subject,the 3D digital model of the arch form including representations of aplurality of the subject's teeth including a 3D digital model of thegiven tooth; identifying an initial tooth position of the given tooth;acquiring an indication of a target tooth position for the given tooth;obtaining a trajectory of the given tooth from the initial toothposition to the target tooth position, the trajectory comprising aplurality of trajectory segments; for a given trajectory segment of theplurality of trajectory segments, applying a force to the 3D digitalmodel of the given tooth to displace the given tooth from a startposition to an end position of the trajectory segment within apredetermined time interval; determining whether the application of theforce to the 3D digital model of the given tooth causes an inducedstress associated with at least one other of the plurality of subject'steeth; in response to a determination that the induced stress is outsideof a predetermined threshold level, determining a counter force to beapplied to the at least one other of the plurality of subject's teeth;determining, for the given trajectory segment, the orthodontic treatmentas including the force to be applied to the given tooth and thedetermined counter force to be applied to the at least one other of theplurality if subject's teeth; and storing data indicative of theorthodontic treatment in a memory communicatively coupled to theprocessor.

In certain embodiments, the predetermined threshold level comprises aminimum stress threshold above which the at least one other of theplurality of subject's teeth is caused to move.

In certain embodiments, the counter force is determined so as to reducea movement of the at least one other of the plurality of subject'steeth.

In certain embodiments, the counter force is determined so as to directa movement of the at least one other of the plurality of subject'steeth.

In certain embodiments, the method further comprises determining theforce to be applied to the 3D digital model of the given tooth, thedetermining comprising: obtaining a minimum stress threshold for thegiven tooth, the minimum stress threshold comprising a minimum amount ofstress required to cause the given tooth to move; obtaining a maximumstress threshold for the given tooth, the maximum stress thresholdcomprising a minimum amount of stress which would cause permanent damageto soft tissues around the given tooth; and determining the force asthat which induces a stress in the given tooth between the minimumstress threshold and the maximum stress threshold.

In certain embodiments, the method further comprises determining one orboth of the minimum stress threshold and the maximum stress threshold ofthe given tooth using a finite element analysis (FEA) method.

In certain embodiments, the predetermined threshold level is that whichavoids inducing movement in the at least one other of the plurality ofsubject's teeth.

In certain embodiments, the predetermined threshold level is that whichdoes not damage the at least one other of the plurality of subject'steeth or soft tissues surrounding the teeth.

In certain embodiments, the predetermined threshold level is that whichcan be countered by an orthodontic appliance to avoid movement of the atleast one other of the plurality of subject's teeth.

In certain embodiments, the predetermined threshold level is determinedbased on a minimum stress threshold of a respective one of the other ofthe plurality of subject's teeth, and a maximum stress threshold of therespective one of the other of the plurality of subject's teeth, theminimum stress threshold comprising a minimum amount of stress requiredto cause the given respective tooth to move, and the maximum stressthreshold comprising a minimum amount of stress which would causepermanent damage to soft tissues around the respective given tooth.

In certain embodiments, the method further comprises determining one orboth of the minimum stress threshold and the maximum stress threshold ofthe given respective tooth using a finite element method on the givenrespective tooth.

In certain embodiments, the method further comprises displaying, on adisplay of the electronic device, the determined orthodontic treatmentof the trajectory segment.

In certain embodiments, the method further comprises causing amanufacture of an orthodontic aligner according to the determinedorthodontic treatment.

From a further aspect, there is provided a system for determining anorthodontic treatment for a tooth of a subject, the system comprising aprocessor of an electronic device, the processor being configured toexecute a method comprising: acquiring a 3D digital model of an archform of the subject, the 3D digital model of the arch form includingrepresentations of a plurality of the subject's teeth including a 3Ddigital model of the given tooth; identifying an initial tooth positionof the given tooth; acquiring an indication of a target tooth positionfor the given tooth; obtaining a trajectory of the given tooth from theinitial tooth position to the target tooth position, the trajectorycomprising a plurality of trajectory segments; for a given segment ofthe plurality of trajectory segments, applying a force to the 3D digitalmodel of the given tooth to displace the given tooth from a startposition to an end position of the trajectory segment within apredetermined time interval, and determining an induced stressassociated with at least one other of the plurality of subject's teeth;in response to a determination that the induced stress is above athreshold level, determining a counter force to be applied to the atleast one other of the plurality of subject's teeth in order to counterthe induced stress; determining, for the given segment, the orthodontictreatment as including the force to the given tooth and the counterforce to the at least one other of the plurality of subject's teeth; andstoring data indicative of the determined orthodontic treatment in amemory communicatively coupled to the processor.

According to another broad aspect of the present technology, there isprovided a method for determining a tooth trajectory in orthodontictreatment for a tooth of a subject, the method being executable by aprocessor of an electronic device. The method comprises acquiring a 3Ddigital model of an arch form of the subject, the 3D digital model ofthe arch form including representations of a plurality of the subject'steeth including a 3D digital model of the given tooth; identifying aninitial tooth position of the given tooth; acquiring an indication of atarget tooth position for the given tooth; obtaining a preliminarytrajectory of the given tooth from the initial tooth position to thetarget tooth position, the preliminary trajectory comprising a pluralityof preliminary trajectory segments; and determining the tooth trajectoryfor the given tooth from the preliminary trajectory by executing anoptimization algorithm on a first preliminary trajectory segment of theplurality of preliminary trajectory segments. The executing theoptimization algorithm comprises applying a first preliminary force tothe 3D digital model of the given tooth to displace the given tooth froma start position to an end position of the first preliminary trajectorysegment within a predetermined time interval; determining a firstinduced stress associated with at least one other of the plurality ofsubject's teeth; in response to a determination that the first inducedstress does not meet a threshold level, modulating the first preliminaryforce such that the first induced stress is modulated to a desirablelevel, thereby determining a first valid force to be applied to thegiven tooth; applying the first valid force to the given tooth at thestart position of the first preliminary trajectory segment to determinea validated end position of the first preliminary trajectory segment,thereby defining a first validated trajectory segment; determining thetooth trajectory of the given tooth as including the first validatedtrajectory segment having the start position and the validated endposition; using the determined tooth trajectory of the given tooth aspart of the orthodontic treatment of the subject; and storing dataindicative of the determined tooth trajectory or the orthodontictreatment in a memory communicatively coupled to the processor.

In certain embodiments, the method comprises determining the firstpreliminary force to be applied to the 3D digital model of the giventooth, the determining comprising: obtaining a minimum stress thresholdfor the given tooth, the minimum stress threshold comprising a minimumamount of stress required to cause the given tooth to move; obtaining anmaximum stress threshold for the given tooth, the maximum stressthreshold comprising a minimum amount of stress which would causepermanent damage to soft tissues around the given tooth; and determiningthe first preliminary force as being a force which would induce a stressin the given tooth between the minimum stress threshold and the maximumstress threshold.

In certain embodiments, the method further comprises determining one orboth of the minimum stress threshold and the maximum stress threshold ofthe given tooth using a finite element analysis (FEA) method.

In certain embodiments, the desirable level of the first transfer forceis that which avoids inducing movement in the at least one other of theplurality of subject's teeth.

In certain embodiments, the desirable level of the first transfer forceis that which does not damage the at least one other of the plurality ofsubject's teeth or soft tissues surrounding the teeth.

In certain embodiments, the desirable level of the first transfer forceis that which can be countered by an orthodontic appliance to avoidmovement of the at least one other of the plurality of subject's teeth.

In certain embodiments, the desirable level of the first transfer forceis determined based on a minimum stress threshold of a respective one ofthe other of the plurality of subject's teeth, and a maximum stressthreshold of the respective one of the other of the plurality ofsubject's teeth, the minimum stress threshold comprising a minimumamount of stress required to cause the given respective tooth to move,and the maximum stress threshold comprising a minimum amount of stresswhich would cause permanent damage to soft tissues around the respectivegiven tooth.

In certain embodiments, the method further comprises determining one orboth of the minimum stress threshold and the maximum stress threshold ofthe given respective tooth using a finite element method on the givenrespective tooth.

In certain embodiments, the method further comprises determining asecond validated trajectory segment, a start position of the secondvalidated trajectory segment comprising the adjusted end position of thefirst validated trajectory segment, and an end position of the secondvalidated trajectory segment being determined by applying a secondpreliminary force to the 3D digital model of the given tooth to displacethe given tooth from the start position of the second validatedtrajectory segment to the end position of the second preliminarytrajectory segment within a predetermined time interval; determiningwhether the application of the second preliminary force to the 3Ddigital model of the given tooth causes a second induced stress to beapplied to at least one other of the plurality of subject's teeth; inresponse to a determination that the second induced stress does not meeta threshold level, modulating the second preliminary force such that thelevel of the second induced stress is modulated to a desirable level,thereby determining a second valid force to be applied to the giventooth; applying the second valid force to the given tooth at the startposition of the second preliminary trajectory segment to determine anadjusted end position of the second preliminary trajectory segment,thereby defining the second validated trajectory segment.

In certain embodiments, the determining the preliminary trajectory ofthe given tooth from the initial tooth position to the target toothposition, comprises determining the plurality of preliminary trajectorysegments so as to minimize a number of segments required to move thegiven tooth from the initial tooth position to the target toothposition.

In certain embodiments, the plurality of preliminary trajectory segmentsof the given tooth each has an equal distance interval or an equal timeinterval.

In certain embodiments, the method further comprises generating, by theoptimization algorithm, respective tooth trajectories for other ones ofthe plurality of subject's teeth, the generating comprising determininga respective preliminary force to be applied to the 3D digital model ofa respective tooth before determining the respective tooth trajectory,the determining comprising: obtaining a minimum stress threshold for therespective tooth, the minimum stress threshold comprising a minimumamount of stress required to cause the respective tooth to move;obtaining a maximum stress threshold for the respective tooth, themaximum stress threshold comprising a minimum amount of stress whichwould cause permanent damage to soft tissues around the respectivetooth; and determining a respective preliminary force to be applied tothe respective tooth and determining the respective preliminary force asbeing a force which would induce a stress in the respective toothbetween the minimum stress threshold and the maximum stress threshold.

In certain embodiments, the method further comprises determining one orboth of the minimum stress threshold value and the maximum stressthreshold of the respective tooth using a finite element method.

In certain embodiments, the method further comprises displaying, on adisplay of the electronic device, the determined tooth trajectory or theplanned orthodontic treatment of the given tooth.

In certain embodiments, the method further comprises displaying, on adisplay of the electronic device, the determined tooth trajectories orthe planned orthodontic treatment of the other ones of the plurality ofsubject's teeth.

In certain embodiments, the method further comprises causing amanufacture of an orthodontic aligner according to the determined toothtrajectory or orthodontic treatment.

From another aspect, there is provided a system for determining a toothtrajectory in orthodontic treatment for a tooth of a subject, the systemcomprising a processor of an electronic device, the processor configuredto execute a method. The method comprises acquiring a 3D digital modelof an arch form of the subject, the 3D digital model of the arch formincluding representations of a plurality of the subject's teethincluding a 3D digital model of the given tooth; identifying an initialtooth position of the given tooth; acquiring an indication of a targettooth position for the given tooth; obtaining a preliminary trajectoryof the given tooth from the initial tooth position to the target toothposition, the preliminary trajectory comprising a plurality ofpreliminary trajectory segments; determining the tooth trajectory forthe given tooth from the preliminary trajectory by executing anoptimization algorithm on a first preliminary trajectory segment of theplurality of preliminary trajectory segments, the executing comprisingapplying a first preliminary force to the 3D digital model of the giventooth to displace the given tooth from a start position to an endposition of the first preliminary trajectory segment within apredetermined time interval; determining whether the application of thefirst preliminary force to the 3D digital model of the given toothcauses a first induced stress associated with at least one other of theplurality of subject's teeth; in response to a determination that thefirst induced stress does not meet a threshold level, modulating thefirst preliminary force such that the first induced stress is modulatedto a desirable level, thereby determining a first valid force to beapplied to the given tooth; applying the first valid force to the giventooth at the start position of the first preliminary trajectory segmentto determine an adjusted end position of the first preliminarytrajectory segment, thereby defining a first validated trajectorysegment; and determining the tooth trajectory of the given tooth asincluding the first validated trajectory segment having the startposition and the validated end position; using the determined toothtrajectory of the given tooth as part of the orthodontic treatment ofthe subject; and storing data indicative of the determined toothtrajectory or the orthodontic treatment in a memory communicativelycoupled to the processor.

In certain embodiments, the system further comprises a manufacturingsystem for manufacturing an orthodontic appliance for implementing theorthodontic treatment.

In the context of the present specification, unless expressly providedotherwise, the term “orthodontic treatment” is broadly referred to asany type of medical intervention aimed at correcting malocclusionsassociated with the teeth of the patient or moving the patient's teethfor any reason, including surgical and non-surgical manipulations, suchas, but not limited to, using one or more of aligners, brackets,multi-strand wires, strips, retainers, and plates. Further, theorthodontic treatment, as referred to herein, may be determinedautomatically by a software, based on image data and other inputsassociated with the subject, or semi-automatically with input from apractitioner such as an orthodontist, a maxillofacial surgeon, forexample.

In the context of the present specification, unless expressly providedotherwise, a computer system may refer, but is not limited to, an“electronic device”, an “operation system”, a “system”, a“computer-based system”, a “controller unit”, a “control device” and/orany combination thereof appropriate to the relevant task at hand.

In the context of the present specification, unless expressly providedotherwise, the expression “computer-readable medium” and “memory” areintended to include media of any nature and kind whatsoever,non-limiting examples of which include RAM, ROM, disks (CD-ROMs, DVDs,floppy disks, hard disk drives, etc.), USB keys, flash memory cards,solid state-drives, and tape drives.

In the context of the present specification, a “database” is anystructured collection of data, irrespective of its particular structure,the database management software, or the computer hardware on which thedata is stored, implemented or otherwise rendered available for use. Adatabase may reside on the same hardware as the process that stores ormakes use of the information stored in the database or it may reside onseparate hardware, such as a dedicated server or plurality of servers.

In the context of the present specification, unless expressly providedotherwise, the words “first”, “second”, “third”, etc. have been used asadjectives only for the purpose of allowing for distinction between thenouns that they modify from one another, and not for the purpose ofdescribing any particular relationship between those nouns.

Embodiments of the present technology each have at least one of theabove-mentioned object and/or aspects, but do not necessarily have allof them. It should be understood that some aspects of the presenttechnology that have resulted from attempting to attain theabove-mentioned object may not satisfy this object and/or may satisfyother objects not specifically recited herein.

Additional and/or alternative features, aspects and advantages ofembodiments of the present technology will become apparent from thefollowing description, the accompanying drawings and the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present technology, as well as otheraspects and further features thereof, reference is made to the followingdescription which is to be used in conjunction with the accompanyingdrawings, where:

FIG. 1 depicts a bottom view of an upper arch form of a subjectexemplifying a misalignment of some of subject's teeth, in accordancewith certain non-limiting embodiments of the present technology;

FIGS. 2A and 2B depict side and cross-sectional views, respectively, ofa personalized dental appliance applied to subject's teeth that may beconfigured to treat the misalignment of the subject's teeth present inFIG. 1 , in accordance with certain non-limiting embodiments of thepresent technology;

FIGS. 3A and 3B schematically depict internal anatomy of a given one ofthe subject's teeth present in FIG. 1 with and without application ofthe personalized dental appliance of FIGS. 2A and 2B, respectively, inaccordance with certain non-limiting embodiments of the presenttechnology;

FIG. 4 depicts a schematic diagram of the upper arch form of FIG. 1 andshowing the misaligned tooth and adjacent teeth, in accordance withcertain embodiments of the present technology;

FIG. 5 depicts a schematic diagram of a system for planning anorthodontic treatment, in accordance with certain embodiments of thepresent technology;

FIG. 6 depicts a schematic diagram of a computing environment of thesystem of FIG. 5 , in accordance with certain embodiments of the presenttechnology;

FIG. 7 depicts a perspective view of a 3D digital model of the upperarch form of FIG. 1 , in accordance with the non-limiting embodiments ofthe present technology;

FIG. 8 depicts a 3D digital model of the given one of the subject'steeth of FIGS. 3A and 3B used, by the processor of FIG. 6 , to implementa method of the present technology, in accordance with the non-limitingembodiments of the present technology;

FIG. 9 depicts an example stress nephogram applied, by the processor ofFIG. 6 , to determine stress thresholds for at least some of thesubject's teeth of FIG. 1 and to implement a method of the presenttechnology, in accordance with certain non-limiting embodiments of thepresent technology;

FIG. 10 depicts a schematic graph illustrating a relationship betweenstress thresholds associated with a tooth, such as one of the teeth ofFIG. 1 , and force applied to the given tooth, in accordance withcertain non-limiting embodiments of the present technology;

FIG. 11 depicts a schematic illustration of the teeth of the upper archform of FIG. 1 with the associated stress thresholds indicated, inaccordance with certain non-limiting embodiments of the presenttechnology;

FIG. 12A depicts a schematic diagram of example preliminary andvalidated tooth trajectories for the misaligned tooth of FIG. 1 and thetwo adjacent teeth, determined by the processor of FIG. 6 , inaccordance with certain non-limiting embodiments of the presenttechnology;

FIG. 12B depicts a schematic diagram of the tooth trajectory of FIG. 12Afor the misaligned tooth of FIG. 1 , the trajectory being sub-dividedinto preliminary trajectory segments, in accordance with certainnon-limiting embodiments of the present technology;

FIG. 13 depicts a flowchart of one aspect of a method for planning theorthodontic treatment based on determining the respective trajectoriesfor the at least some of the subject's teeth of FIG. 1 , in accordancewith certain embodiments of the present technology; and

FIG. 14 depicts a flowchart of another aspect of the method for planningthe orthodontic treatment based on determining the respectivetrajectories for the at least some of the subject's teeth of FIG. 1 , inaccordance with certain embodiments of the present technology.

DETAILED DESCRIPTION

Certain aspects and embodiments of the present technology are directedto methods of and systems for developing at least a portion of anorthodontic treatment for a patient (also referred to herein as a“subject”) which take into account certain safety and efficiencyconsiderations. For the avoidance of doubt, “developing an orthodontictreatment” also encompasses validating, refining or optimizing apreliminary orthodontic treatment. The orthodontic treatment maycomprise a number of successive treatment segments, each treatmentsegment defined by a respective trajectory segment representing movementof respective teeth within that treatment segment. Each treatmentsegment is associated with a predetermined treatment interval. In thisrespect, certain aspects and embodiments of the present technology aredirected to methods of and systems for determining at least onetrajectory segment of the orthodontic treatment.

More specifically, certain aspects and embodiments of the presenttechnology include consideration of a force applied to a given tooth ofthe subject during the treatment segment, as well as transfer forcesinduced by the applied force on at least one other tooth of the patient.The transfer forces may induce movement in the other teeth or damagethereto.

For example, by implementing certain embodiments of the presenttechnology to determine the tooth trajectory for the given tooth, it maybe possible to determine an orthodontic treatment for the patient whichis both safe and efficient. This can be achieved, in certainnon-limiting embodiments of the present technology, by determining anoptimized force to be applied to the given tooth which takes intoaccount stress thresholds of tissues around the given tooth as well asstress thresholds of tissues around other teeth of the same arch form ofthe patient. Stress threshold considerations may include any one or moreof: (a) avoiding or minimizing damage to the given tooth and tissuesaround the given tooth; (b) avoiding and/or minimizing damage to theother teeth and tissues of the same arch form of the patient; and (c)avoiding or mitigating induced movements of the other teeth throughtransfer forces from the force applied to the given tooth. Optimizationmay also take into account minimizing a duration of a given treatmentsegment, minimizing an overall duration of the orthodontic treatment, orminimizing a number of treatment segments whilst taking into account theabove safety considerations.

Certain aspects and embodiments of the present technology will now bedescribed below with reference to the upper teeth 16 of an upper archform 20 of the subject (FIG. 1 ). However, it will be appreciated thatembodiments of the present technology can be applied to any other teethof any other arch form of the patient.

Orthodontic Appliances

Referring initially to FIG. 1 , there is depicted a bottom view of theupper arch form 20 of the patient, to which certain aspects andnon-limiting embodiments of the present technology may be applied.

As it can be appreciated, the upper arch form 20 includes the upperteeth 16 and upper gingiva 36. The upper teeth 16 include a tooth 15which is misaligned, a first adjacent tooth 13 and a second adjacenttooth 17. As can be seen in FIG. 1 , the tooth 15 is positionedoutwardly relative to its neighboring teeth: the first adjacent tooth 13and the second adjacent tooth 17. Thus, for the purposes of describingembodiments of the present technology, the orthodontic treatment to bedetermined for the patient is that of correcting the misalignment of thetooth 15, i.e. moving the tooth 15 from a start position shown in FIG. 1to a target position in which the tooth 15 is aligned with itsneighboring teeth.

In accordance with certain non-limiting embodiments of the presenttechnology, the determined orthodontic treatment may comprise applyingone or more orthodontic devices in the one or more treatment segments tothe upper arch form 20. Generally speaking, the orthodontic device maybe configured to exert a force onto the tooth 15 causing it to movetowards the target position, that is, in the depicted embodiments ofFIG. 1 , inwardly between the first adjacent tooth 13 and the secondadjacent tooth 17 to align with the first adjacent tooth 13 and thesecond adjacent tooth 17. The tooth 15 may be caused to move to thetarget position in one or more treatment segments. In variousnon-limiting embodiments of the present technology, the orthodonticdevice may comprise orthodontic appliances of different types, shapes,sizes and configurations, such as those including, without limitation,aligners, brackets, multi-strand wires, strips, retainers, and plates.

In specific non-limiting embodiments of the present the presenttechnology, the orthodontic device may include an aligner. Withreference to FIGS. 2A and 2B, there is depicted an aligner 10 applied toat least some of the upper teeth 16, in accordance with certainnon-limiting embodiments of the present technology. The aligner 10comprises an inner surface 12 and an outer surface 14. The inner surface12 defines a channel 18, which is configured, in some non-limitingembodiments of the present technology, for receiving crown portions 26(illustrated in FIGS. 3A and 3B) of at least some of the upper teeth 16including the tooth 15, the first adjacent tooth 13, and the secondadjacent tooth 17. However, in other non-limiting embodiments of thepresent technology, the channel 18 of the aligner 10 may be configuredto receive crown portions 26 of all of the upper teeth 16. At least oneedge of the channel 18 is shaped for following a gum line 22 along theupper gingiva 36.

In accordance with the non-limiting embodiments of the presenttechnology, a size, a form factor (such as a U-shape or a V-shape, forexample), and a configuration of the aligner 10, including a materialand a thickness thereof, depend generally on a particular malocclusiondisorder of the patient (such as the misalignment of the tooth 15 withinthe upper teeth 16) or the determined orthodontic treatment for themalocclusion. As an example, in some non-limiting embodiments of thepresent technology, the thickness of the aligner 10 may be about 0.7 mm.In other non-limiting embodiments of the present technology, thethickness is selected from 0.7 mm, 0.75 mm, 0.8 mm, 0.85 mm, 0.9 mm,0.95 mm, and 1.0 mm. In yet other non-limiting embodiments of thepresent technology, the aligner 10 may have regions of variablethickness, such as in interdental regions 24 or occular regions, as anexample.

According to certain non-limiting embodiments of the present technology,the aligner 10 may be made of a polymer, such as a thermoplasticmaterial. In other non-limiting embodiments of the present technology,the aligner 10 may be made of poly-vinyl chloride (PVC). In yet othernon-limiting embodiments of the present technology, the aligner 10 maybe made of polyethylene terephthalate glycol (PETG). Other suitablematerials can also be used to form the aligner 10.

It is to be appreciated that, in accordance with certain non-limitingembodiments of the present technology, the aligner 10 may be used fortreating different types of teeth misalignment or malocclusion,including but not limited to one or more of: closing gaps (“spaceclosure”), creating/widening gaps, tooth rotation, toothintrusion/extrusion, and tooth translation, to name a few. It shouldfurther be noted that in certain non-limiting embodiments of the presenttechnology, applying the aligner 10 to the upper teeth 16 may furtherinclude applying specific attachments (also known as “fixing blocks”)thereto.

The aligner 10 is configured in such a way that its inner surface 12imposes contacts to impose a desired force on one or more of the upperteeth 16 to obtain the target position of the one or more upper teeth 16at a given stage of the orthodontic treatment.

Needles to say, that although in the depicted embodiments of FIGS. 2Aand 2B the aligner 10 is configured to be applied to the upper teeth 16,in other non-limiting embodiments of the present technology, the aligner10 may be configured to be applied to teeth of a lower arch form of thepatient.

Orthodontic Treatment

Efficiency Considerations

In order to cause the tooth 15 to reach the target position, thedetermined orthodontic treatment may comprise a number of sequentialtreatment steps in which a number of different aligners 10 are appliedto the teeth 16. Sequential treatment steps may be required to movedifferent teeth at different times to achieve respective targetpositions (e.g. by avoiding collisions or by creating space for otherteeth to move into), to sub-divide a trajectory of a given tooth intointervals to stay within safety limitations, to sub-divide a trajectoryof a given tooth to avoid collisions or to create space.

Thus, referring back to FIG. 1 and for the specific configuration of theteeth 16 shown in FIG. 1 , in order to cause the tooth 15 to reach thetarget position, the determined orthodontic treatment may comprisesequential treatment steps in which different aligners 10 aresequentially applied to the teeth 16. For example, in the sequentialtreatment steps, the upper teeth 16, other than the tooth 15, may befirst moved to create a space around the tooth 15, and then the tooth 15caused to move inwardly into the space towards the target positionwithin the upper teeth 16.

In determining the orthodontic treatment and more specifically a giventrajectory of the given tooth, certain embodiments of the presenttechnology may take into account an efficiency of orthodontic treatment.By efficiently is meant either in as few sequential orthodontictreatment steps to achieve the target position, or as short a time aspossible from starting the orthodontic treatment to attaining the targetposition. The efficiency of the orthodontic treatment may increase thechances of the patient's adherence to the orthodontic treatment andhence its success and can also minimize certain costs associated withthe orthodontic treatment. However, efficiency must be consideredalongside safety.

Safety Considerations

Biomechanical processes allowing a given one of the upper teeth 16 tomove in the course of the orthodontic treatment, such as the tooth 15towards the target position, under the respective force imposed by thealigner 10 will now be described with reference to FIGS. 3A and 3B.

FIG. 3A depicts a cross-sectional view of the tooth 15 schematicallyillustrating some surrounding tissues thereof, in accordance withcertain non-limiting embodiments of the present technology. As the tooth15 is on the upper arch form 20, the crown portion is depicted asextending downwardly. FIG. 3B depicts the same cross-sectional view ofthe tooth 15 under a force 40 exerted by the aligner 10 (the aligner 10is omitted for clarity).

The tooth 15 includes the crown portion 26 and a root portion 28.Tissues of a periodontium 30 surrounding and supporting the tooth 15include the upper gingiva 36, an alveolar bone 32, and a periodontalligament (PDL) 34. The PDL 34 surrounds the root portion 28 and attachesthe tooth 15 to the alveolar bone 32. As it can be appreciated from FIG.3B, the aligner 10 causes the force 40 to be applied to the crownportion 26 of the tooth 15, which may cause the tooth 15 to pitch,causing compression of the PDL 34 on a compressed portion 42 of the rootportion 28, and tension of the PDL 34 on a strained portion 44 of theroot portion 28. Resultant remodelling of the alveolar bone 32surrounding the tooth 15, with bone resorption of the alveolar bone 32occurring on the compressed portion 42, and bone deposition of thealveolar bone 32 on the strained portion 44, causes the tooth 15 to bedisplaced.

The force 40 directly applied to the tooth 15 by the aligner 10 can bedefined by force parameters such one or more of: a magnitude of thedirectly applied force 40, a duration of the directly applied force 40,a direction of the force 40, a surface area on the tooth 15 to which theforce 40 is applied, and a position on the crown portion 26 of the tooth15 to which the force is applied. The force 40 may also be defined interms of induced stresses in the PDL 34, for example, an induced stressin the PDL 34 of the tooth 15 to which the force 40 is being applied.

The PDL 34 of the tooth 15 can be considered as having a minimum stressthreshold, below which the tooth 15 will not move. Therefore, for thetooth 15 to move, the induced stress in the PDL 34 must be above theminimum stress threshold. A magnitude of the minimum stress threshold ofthe PDL 34 may be associated with certain parameters of the appliedforce 40 to the tooth. Furthermore, the minimum stress threshold of PDLs34 of different teeth may vary from one another. Different teeth withdiffering surface area likely have a different volume of periodontalligament.

The PDL 34 of the tooth 15 can also be considered as having a maximumstress threshold, beyond which the PDL 34 or other tissues of theperiodontium 30 will be damaged. The maximum stress threshold of the PDL34 may be associated with certain parameters of the force 40 applied tothe tooth 15. The damage may include resorption of the root portion 28;necrosis in the upper gingiva 36 through excess compression of proximalblood vessels and nerve pathways; damage to the PDL; pain; pulpalchanges; periodontal disease such as gingivitis, loss of the alveolarbone 32, periodontitis, and the like, to name a few.

Developers have appreciated that certain forces 40 which are applied mayalso result in induced stresses in the PDLs of other teeth (i.e. otherthan the tooth 15) through the force 40 applied to the given tooth beingtransferred to other teeth of the same arch form. Such transferredforces are herein referred to as “transfer forces”.

The induced stresses in the PDLs 34 of the other teeth are associatedwith certain parameters of the force 40 applied to the tooth 15 as wellas relative configuration of the other teeth to the tooth 15 to whichthe force is being applied. For example, the tooth 13 and the tooth 17may have higher induced stresses, induced from the force 40 beingapplied to the tooth 15, than other teeth 16 of the arch form which arefurther from the tooth 15. Also, higher induced stresses of the tooth 13and the tooth 17 may be obtained with a force 40 of higher magnitude.

In certain embodiments, a potential consequence of the transfer force isunintentional or undesired tooth movements for certain teeth for whichthe induced stress in their respective PDLs 34 exceeds the minimumstress threshold.

For example, and with reference to FIG. 4 , there is shown a plan viewof the upper arch form 20 of FIG. 1 showing the tooth 13, the tooth 15and the tooth 17, and with all other upper teeth 16 omitted for clarity.Applying the force 40 to the tooth 15 causes an induced stress in thePDL 34 of the tooth 15 which is greater than the minimum stressthreshold of the PDL 34 causing the tooth 15 to move from the startposition S₁₅ towards the target position T₁₅. The applied force 40 alsoinduces transfer forces to the tooth 13 and the tooth 17. The transferforces induce a stress in the PDL 34 of the tooth 17 which is higherthan its minimum stress threshold thereby also causing the tooth 17 tomove from the start position S₁₇ to the position T₁₇. However, thetransfer forces induce a stress in the PDL 34 of the tooth 13 which islower than its minimum stress threshold thereby the tooth 13 is notaffected.

Therefore, according to certain embodiments of the present technology,in determining the orthodontic treatment and hence the configuration ofthe aligner 10, embodiments of the present technology take into accountsuch transfer forces.

Thus, non-limiting embodiments of the present technology describedherein are directed to determining a tooth trajectory of a given toothwithin a given treatment segment (referred to herein as a “trajectorysegment”) which optimizes the force 40 applied to it by the orthodonticappliance and takes into account the above safety considerations, andparticularly transfer forces on at least some of the teeth of the samearch form other than the given tooth, and as well as, optionally, anefficiency of the orthodontic treatment.

How the trajectory segment is thus determined, and how it may be usedfor planning the orthodontic treatment, according to certainnon-limiting embodiments of the present technology, will be describedwith reference to systems and methods described below and with referenceto FIGS. 5 to 13 .

System

Referring to FIGS. 5 and 6 , there is depicted a schematic diagram of asystem 500 suitable for determining the tooth trajectory of a giventooth, such as the tooth 15, for planning the orthodontic treatment, inaccordance with certain non-limiting embodiments of the presenttechnology.

It is to be expressly understood that the system 500 as depicted ismerely an illustrative implementation of the present technology. Thus,the description thereof that follows is intended to be only adescription of illustrative examples of the present technology. Thisdescription is not intended to define the scope or set forth the boundsof the present technology. In some cases, what is believed to be helpfulexamples of modifications to the system 500 may also be set forth below.This is done merely as an aid to understanding, and, again, not todefine the scope or set forth the bounds of the present technology.These modifications are not an exhaustive list, and, as a person skilledin the art would understand, other modifications are likely possible.Further, where this has not been done (i.e., where no examples ofmodifications have been set forth), it should not be interpreted that nomodifications are possible and/or that what is described is the solemanner of implementing that element of the present technology. As aperson skilled in the art would understand, this is likely not the case.In addition, it is to be understood that the system 500 may provide incertain instances simple implementations of the present technology, andthat where such is the case they have been presented in this manner asan aid to understanding. As persons skilled in the art would furtherunderstand, various implementations of the present technology may be ofa greater complexity.

Broadly the system 500 of FIG. 5 comprises a computer system 510 havingat least one interface device 520 for providing an input or an output toa user of the system 500. The system may further comprise an imagingdevice 530 communicatively coupled to the computer system 510, andoptionally a manufacturing system 540 for making an orthodonticappliance, such as the aligner 10.

Computer System

In certain non-limiting embodiments of the present technology, thecomputer system 510 may be configured, by pre-stored programinstructions, to generate, based on image data associated with thepatient, the orthodontic treatment for the patient. More specifically,the computer system 510 may be configured to determine at least one of anumber of successive treatment segments, each treatment segment definedby trajectory segments representing movement of respective teeth withinthat treatment segment.

To that end, in some non-limiting embodiments of the present technology,the computer system 510 is configured to receive image data pertainingto the patient or to a given stage of the orthodontic treatment.According to some non-limiting embodiments of the present technology,the computer system 510 may receive the image data via localinput/output interface (such as USB, as an example, not separatelydepicted). In other non-limiting embodiments of the present technology,the computer system 510 may be configured to receive the image data overa communication network 525, to which the computer system 510 iscommunicatively coupled.

In some non-limiting embodiments of the present technology, thecommunication network 525 is the Internet and/or an Intranet. Multipleembodiments of the communication network may be envisioned and willbecome apparent to the person skilled in the art of the presenttechnology. Further, how a communication link between the computersystem 510 and the communication network 525 is implemented will depend,inter alia, on how the computer system 510 is implemented, and mayinclude, but is not limited to, a wire-based communication link and awireless communication link (such as a Wi-Fi communication network link,a 3G/4G communication network link, and the like).

It should be noted that the computer system 510 can be configured forreceiving the image data from a vast range of devices. Some of suchdevices can be used for capturing and/or processing data pertaining tomaxillofacial and/or cranial anatomy of the patient. In certainembodiments, the image data received from such devices is indicative ofproperties of anatomical structures of the patient, including: teeth,intraoral mucosa, maxilla, mandible, temporomandibular joint, and nervepathways, among other structures. In some non-limiting embodiments ofthe present technology, at least some of the image data is indicative ofproperties of external portions of the anatomical structures, forexample dimensions of a gingival sulcus, and dimensions of an externalportion of a tooth (e.g., a crown of the tooth) extending outwardly ofthe gingival sulcus. In some embodiments, the image data is indicativeof properties of internal portions of the anatomical structures, forexample volumetric properties of bone surrounding an internal portion ofthe tooth (e.g., a root of the tooth) extending inwardly of the gingivalsulcus. Under certain circumstances, such volumetric properties may beindicative of periodontal anomalies which may be factored into anorthodontic treatment plan. In some non-limiting embodiments of thepresent technology, the image data includes cephalometric imagedatasets. In some embodiments, the image data includes datasetsgenerally intended for the practice of endodontics. In some embodiments,the image data includes datasets generally intended for the practice ofperiodontics.

In alternative non-limiting embodiments of the present technology, thecomputer system 510 may be configured to receive the image dataassociated with the patient directly from the imaging device 530communicatively coupled thereto.

Imaging Device

Broadly speaking the imaging device 530 may be configured to captureand/or process the image data of the upper teeth 16 and the periodontium(not depicted) of the patient. In certain non-limiting embodiments ofthe present technology, the image data may include, for example, one ormore of: (1) images of external surfaces of respective crown portions(such as the crown portion 26 of the tooth 15) of the upper teeth 16,(2) images of an external surface of the periodontium including those ofthe upper gingiva (not depicted), the alveolar maxillary bone (notdepicted), and images of superficial blood vessels and nerve pathwaysassociated with the upper teeth 16; and (3) images of an oral region. Bydoing so, the imaging device 530 may be configured, for example, tocapture image data of the upper arch form 20 of the patient. In anotherexample, the imaging device may also be configured to capture and/orprocess image data of a lower arch form associated with the patientwithout departing from the scope of the present technology. It should benoted that the image data may include two-dimensional (2D) data and/orthree-dimensional data (3D). Further, in certain non-limitingembodiments of the present technology, the image data includes 2D data,from which 3D data may be derived, and vice versa.

In some non-limiting embodiments of the present technology, the imagingdevice 530 may comprise an intra-oral scanner enabling to capture directoptical impressions of the upper arch form 20 of the patient.

In a specific non-limiting example, the intraoral scanner can be of oneof the types available from MEDIT, corp. of 23 Goryeodae-ro 22-gil,Seongbuk-gu, Seoul, South Korea. It should be expressly understood thatthe intraoral scanner can be implemented in any other suitableequipment.

In other non-limiting embodiments of the present technology, the imagingdevice 530 may comprise a desktop scanner enabling to digitize a moldrepresenting the upper arch form 20. In this regard, the mold may havebeen obtained via dental impression using a material (such as a polymer,e.g. polyvinyl-siloxane) having been imprinted with the shape of theintraoral anatomy it has been applied to. In the dental impression, aflowable mixture (i.e., dental stone powder mixed with a liquid incertain proportions) may be flowed such that it may, once dried andhardened, form the replica.

In a specific non-limiting example, the desktop scanner can be of one ofthe types available from Dental Wings, Inc. of 2251, ave Letourneux,Montreal (QC), Canada, H1V 2N9. It should be expressly understood thatthe desktop scanner can be implemented in any other suitable equipment.

In yet other non-limiting embodiments of the present technology, theimaging device 530 may comprise a cone beam computed tomography (CBCT)scanner. Generally speaking, the CBCT scanner comprises software andhardware allowing for capturing data using a cone-shaped X-ray beam byrotating around the patient's head. This data may be used to reconstruct3D representations of the following regions of the patient's anatomy:dental (teeth and gum, for example); oral and maxillofacial region(mouth, jaws, and neck); and ears, nose, and throat (“ENT”).

In a specific non-limiting example, the CBCT scanner can be of one ofthe types available from 3Shape, Private Limited Company of HolmensKanal 7, 1060 Copenhagen, Denmark. It should be expressly understoodthat the CBCT scanner can be implemented in any other suitableequipment.

Further, it is contemplated that the computer system 510 may beconfigured for processing of the received image data. The resultingimage data of the upper arch form 20 received by the computer system 510is typically structured as a binary file or an ASCII file, may bediscretized in various ways (e.g., point clouds, polygonal meshes,pixels, voxels, implicitly defined geometric shapes), and may beformatted in a vast range of file formats (e.g., STL, OBJ, PLY, DICOM,and various software-specific, proprietary formats). Any image data fileformat is included within the scope of the present technology. Forimplementing functions described above, the computer system 510 mayfurther comprise a corresponding computing environment.

Computing Environment

With reference to FIG. 6 , there is depicted a schematic diagram of acomputing environment 640 suitable for use with some implementations ofthe present technology. The computing environment 640 comprises varioushardware components including one or more single or multi-coreprocessors collectively represented by the processor 650, a solid-statedrive 660, a random-access memory 670 and an input/output interface 680.Communication between the various components of the computingenvironment 640 may be enabled by one or more internal and/or externalbuses 690 (e.g. a PCI bus, universal serial bus, IEEE 1394 “Firewire”bus, SCSI bus, Serial-ATA bus, ARINC bus, etc.), to which the varioushardware components are electronically coupled.

The input/output interface 680 allows enabling networking capabilitiessuch as wire or wireless access. As an example, the input/outputinterface 680 comprises a networking interface such as, but not limitedto, a network port, a network socket, a network interface controller andthe like. Multiple examples of how the networking interface may beimplemented will become apparent to the person skilled in the art of thepresent technology. For example, but without being limiting, theinput/output interface 680 may implement specific physical layer anddata link layer standard such as Ethernet™, Fibre Channel, Wi-Fi™ orToken Ring. The specific physical layer and the data link layer mayprovide a base for a full network protocol stack, allowing communicationamong small groups of computers on the same local area network (LAN) andlarge-scale network communications through routable protocols, such asInternet Protocol (IP).

According to implementations of the present technology, the solid-statedrive 660 stores program instructions suitable for being loaded into therandom-access memory 670 and executed by the processor 650, according tocertain aspects and embodiments of the present technology. For example,the program instructions may be part of a library or an application.

In some non-limiting embodiments of the present technology, thecomputing environment 640 is implemented in a generic computer system,which is a conventional computer (i.e. an “off the shelf” genericcomputer system). The generic computer system may be a desktopcomputer/personal computer, but may also be any other type of electronicdevice such as, but not limited to, a laptop, a mobile device, a smartphone, a tablet device, or a server.

As persons skilled in the art of the present technology may appreciate,multiple variations as to how the computing environment 640 can beimplemented may be envisioned without departing from the scope of thepresent technology.

Interface Device

Referring back to FIG. 5 , the computer system 510 has the at least oneinterface device 520 for providing an input or an output to a user ofthe system 500, the interface device 520 being in communication with theinput/output interface 680. In the embodiment of FIG. 5 , the interfacedevice 520 is a screen 552. In other non-limiting embodiments of thepresent technology, the interface device 520 may be a monitor, aspeaker, a printer or any other device for providing an output in anyform such as an image form, a written form, a printed form, a verbalform, a 3D digital model form, or the like.

In the depicted embodiments of FIG. 5 , the interface device 520 alsocomprises a keyboard 524 and a mouse 526 for receiving input from theuser of the system 500. Other interface devices 520 for providing aninput to the computer system 510 can include, without limitation, a USBport, a microphone, a camera or the like.

The computer system 510 may be connected to other users, such as throughtheir respective clinics, through a server (not depicted). The computersystem 510 may also be connected to stock management or client softwarewhich could be updated with stock when the orthodontic treatment hasbeen determined and/or schedule appointments or follow-ups with clients,for example.

Manufacturing System

The system 500 could, in some embodiments, further include themanufacturing system 540 for making the aligner 10, operativelycommunicable with the computer system 510. While described as beinggenerally co-located with other portions of the system 500, it is alsocontemplated that the manufacturing system 540 could be disposed at aseparate location and be communicatively connected to remaining portionsof the system 500 as described above, such as by an internet connection.In some such implementations, the computer system 510 could sendmanufacturing instructions to the manufacturing system 540, for example.Details relating to the manufacturing system and processes implementedtherewith will be described briefly herein. Further information can befound in U.S. Pat. No. 10,717,208, entitled “METHODS AND SYSTEMS FORTHERMOFORMING ORTHODONTIC ALIGNERS”, issued on Jul. 21, 2020, theentirety of which is incorporated herein by reference.

In certain embodiments, the manufacturing system 540 includes athermoforming device for shaping a precursor aligner into the aligner 10using an aligner mold and a precursor aligner. The thermoforming deviceis configured to receive the aligner mold and the precursor aligner, andto shape the precursor aligner onto the aligner mold during athermoforming operation, in which heat and pressure imparted to theprecursor aligner during shaping are controlled.

In some embodiments, the manufacturing system 540 further includes acomputer-assisted post-processing device such as a computer numericalcontrol (CNC) milling device or a CNC laser cutting device for furthershaping the aligner 10 into a post-processed aligner (not shown). Thepost-processing of the aligner 10 may include one or both of (i) formingrecesses or openings in the aligner body, and (ii) forming an edge ofthe channel 18. In some such embodiments, the post-processing device isoperatively connectable to the computer system 510 for receivingoperating instructions from the computer system 510 for post-processingthe aligner 10. The operating instructions may for example be derivedfrom a digital model indicative of a desired aligner (not shown).

In some embodiments, the manufacturing system 540 further includes anauxiliary manufacturing device for making the aligner mold. Theauxiliary manufacturing device is an additive manufacturing device, alsoreferred to in some cases as a 3-D printing device. It is alsocontemplated that, in other embodiments, a CNC milling device may beused instead. In certain embodiments, an auxiliary manufacturing devicemay be used for making precursor aligners, for example an additivemanufacturing device arranged for fabricating customized precursoraligners.

In some embodiments, the computer system 510 is configured to receiveimage data from the imaging device 530 pertaining to the patient or to agiven orthodontic treatment (such as a digital model of the aligner 10).The computer system 510 may use the image data for determining thethermoforming parameters. In certain embodiments, the computer system510 is arranged to determine an orthodontic treatment using the imagedata.

In certain non-limiting embodiments, the system 500 further includes arobotic system arranged relative to the thermoforming device, forhandling one or more of the aligner mold, the precursor aligner, and thealigner 10. In some non-limiting embodiments, the robotic system couldbe omitted.

In certain embodiments, the system 500 and/or computer system 510 couldbe connectable to one or more of the imaging device 530, thethermoforming device, the post-processing device, the auxiliarymanufacturing device and the robotic system (where included) via acommunication network. In some embodiments, the communication network isthe Internet and/or an Intranet. Multiple embodiments of thecommunication network may be envisioned and would be apparent to theperson skilled in the art of the present technology.

Orthodontic Treatment Planning

As previously alluded to, according to the non-limiting embodiments ofthe present technology, the processor 650 may be configured to: (1)receive the image data associated with the patient's teeth, such as theupper teeth 16; (2) based on the received image data, determine, for atleast some of the upper teeth 16, a respective tooth trajectory, forexample, the tooth trajectory of the tooth 15 which respects certainsafety considerations of at least some of the upper teeth 16; (3) basedon the so determined tooth trajectory, determine the orthodontictreatment for the patient; and one or more of (4i) cause the manufactureof an orthodontic appliance for applying the orthodontic treatment, suchas the aligner 10, (4ii) cause the display of the determined orthodontictreatment, and (4iii) save the determined orthodontic treatment.

3D Digital Models

According to some non-limiting embodiments of the present technology,having received the image data, the processor 650 may be configured togenerate 3D digital models of one or more arch forms of the patient.Alternatively, the processor 650 may be configured to receive the 3Ddigital models of the one or more arch forms of the patient, such asfrom the imaging device 530 or from the memory.

With reference to FIG. 7 , there is depicted a perspective view of a 3Ddigital model 700 representing a configuration of the upper arch form 20of the patient prior to applying the orthodontic treatment, inaccordance with the non-limiting embodiments of the present technology.

More specifically, the 3D digital model 700 of the upper arch form 20depicts a representation of outer surfaces of the upper teeth 16 and theupper gingiva 36. As it can be appreciated, the upper teeth 16 arerepresented, in the 3D digital model 700, by respective crown portionsassociated therewith, such as the crown portion 26 of the tooth 15.

The 3D digital model 700 may have any appropriate format such as a mesh,point cloud, etc. In certain embodiments, the 3D digital model 700 ofthe upper arch form 20 comprises a plurality of mesh elements (notdepicted) representative of a surface of the upper arch form 20. Theplurality of mesh elements may include, without limitation, triangularmesh elements, quadrilateral mesh elements, convex polygonal meshelements, or even concave polygonal mesh elements, as an example,without departing from the scope of the present technology.

The 3D digital model 700 may include a coordinate system 750 associatedwith the 3D digital model 700. In one non-limiting example, theprocessor 650 may be configured to determine the coordinate system 750such that an XY plane thereof is parallel to a transverse planeassociated with a patient's skull (not depicted). In another example,the XY plane may be parallel to a Frankfort horizontal plane associatedwith the patient's cranium (not depicted).

In some non-limiting embodiments of the present technology, theprocessor 650 may be configured to cause segmentation of the 3D digitalmodel 700 of the upper arch form 20 in order to determine boundariesbetween crown portions of adjacent teeth, and/or boundaries between agiven tooth and a surrounding gingiva, thereby generating a plurality ofso isolated crown portions associated with at least one tooth of theupper arch form 20.

To that end, according to some non-limiting embodiments of the presenttechnology, the processor 650 may be configured to apply one or moreapproaches to automatic tooth segmentation, for example, that which isdescribed in a co-owned U.S. Pat. No. 10,695,147-B1, entitled “METHODAND SYSTEM FOR DENTAL BOUNDARY DETERMINATION”, issued Jun. 30, 2020; thecontent of which is hereby incorporated by reference in its entirety.

How the processor 650 can be configured to isolate the crown portion isnot limited; and, in some non-limiting embodiments of the presenttechnology, the processor 650 can be configured to apply, to the 3Ddigital model 700, one or more automatic tooth segmentation approachesdescribed in a co-owned U.S. Pat. No. 10,888,397-B1 issued on Jan. 12,2021, entitled “METHOD AND SYSTEM FOR DENTAL BOUNDARY DETERMINATION”,content of which is incorporated herein by reference in its entirety.

Further, in some non-limiting embodiments of the present technology,using the so generated segmented crown portions associated with the atleast one tooth of the upper arch form 20, the processor 650 may furtherbe configured to model tooth movements of at least some of the upperteeth 16 of the upper arch form 20 to determine the orthodontictreatment.

In additional non-limiting embodiments of the present technology, for amore effective modeling of the movements of the given tooth, such as thetooth 15, by applying respective forces thereto (such as the force 40),the processor 650 may be configured to augment the 3D digital model 700,such as the crown portion 26 of the tooth 15 separated from surroundinggingiva 36. Augmenting the 3D digital model 700 may include one or moreof: (1) augmenting the 3D digital model of the crown portion 26 with areconstructed 3D digital model of the root portion 28 (for example, inthose embodiments where the imaging device 530 is the intra-oral scannerused for generating the 3D digital model 700 and which does not captureany image data pertaining to the root portion 28); (2) augmenting the 3Ddigital model 700 of the crown portion 26 with a reconstructed surfaceto remove artefacts; and (3) augmenting the 3D digital model 700 of thearch form 20 with a reconstructed gingival surface to remove artefacts.

To that end, according to certain non-limiting embodiments of thepresent technology, the processor 650 may be configured to apply certaintooth reconstruction techniques described in a co-owned U.S. Pat. No.11,026,767-B1, issued on Jun. 8, 2021 and entitled “SYSTEMS AND METHODSFOR PLANNING AN ORTHODONTIC TREATMENT”, the content of which isincorporated hereby by reference in its entirety.

FIG. 8 depicts a tooth 3D digital model 800 of the tooth 15 derived fromthe 3D digital model 700 of FIG. 7 , in accordance with certainnon-limiting embodiments of the present technology. The tooth 3D digitalmodel 800 includes a crown 3D representation 806 of the crown portion 26and optionally a root 3D representation 808 of the root portion 28. Thetooth 3D digital model 800 may have been generated by the processor 650or obtained by other means. The processor 650 may have generated thetooth 3D digital model 800 based on the methods described above andincorporated by reference herein, or in any other manner.

The processor 650 may be configured to use the tooth 3D digital model800 for one or more of: modelling forces applied to the tooth 15,determining stress thresholds of the tooth 15, and determining thetransfer forces of the other teeth.

Determining Stress Thresholds

In accordance with certain non-limiting embodiments of the presenttechnology, the processor 650 may be configured to determine the stressthresholds associated with the tooth 15, as well as the other teeth ofthe upper arch form 20. In other embodiments, the processor 650 may beconfigured to obtain the stress thresholds from a memory of a computersystem, such as the memory 670.

Referring back to FIGS. 3A and 3B, in the context of the presentspecification, the term “stress thresholds” includes one or more of aminimum stress threshold, a maximum stress threshold, and an optimalstress threshold. The minimum stress threshold denotes a minimum amountof stress that must be applied to the tissues of the periodontium 30 ofthe given tooth, such as the tooth 15 or the other teeth 16 of the archform 20, to cause the given tooth to move.

At the minimum stress threshold, the PDL 34 may start the process ofbone remodeling. Stresses that occur less than the minimum stressthreshold are perceived as normal load on the given tooth and when suchstresses occur, restructuring of bone tissue does not occur. Any toothmovement occurring due to induced stresses lower than the minimum stressthreshold may be considered reversible.

The maximum stress threshold denotes a maximum amount of stress that canbe applied to the tissues of the periodontium 30 of the given tooth,such as the tooth 15 or the other teeth 16 of the arch form 20, beforecausing possibly irreversible damage to the periodontium 30. Forexample, bone tissue restructuring at these high stresses may beirreversible and PDL 34 recovery may not be possible or require longrecovery times.

The optimal stress threshold denotes an optimal amount of stress thatcan be applied to the tissues of the periodontium 30 of the given tooth,such as the tooth 15 or the other teeth 16 of the arch form 20, at whichbone restructuring occurs but without damage to the PDL 34.

According to certain non-limiting embodiments of the present technology,the processor 650 may be configured to determine the stress thresholdsassociated with the teeth 16, such as the tooth 15, the tooth 13 and thetooth 17. The processor may 650 may also be configured to determineassociated forces to be applied to the teeth based on the stressthresholds.

In certain embodiments, the processor 650 is configured to determine thestress thresholds based on a Stress Cumulative Distribution Function(SCDF). In some non-limiting embodiments of the present technology, theSCDF may be predetermined for each of the upper teeth 16, such as thetooth 15, empirically, based on analyzing deformation features of theperiodontium 30 under various external forces. Further, in specificnon-limiting embodiments of the present technology, the analyzing thedeformation forces may include analyzing a finite element model of thetooth 15, which the processor 650 may be configured to generate based onthe tooth 3D digital model 800. Broadly speaking, in these embodiments,the SCDF may be configured to return a portion of a surface of the PDL34, where stress is greater than an amount of stress of interest causedby a given external force. Thus, according to certain non-limitingembodiments of the present technology, the SCDF may be formalized by thefollowing equation:SCDF(F _(i) ,s _(i))=S _(i)(PDL),  (1)

where F_(i) is an external force (e.g. the force 40 applied to the tooth15);

-   -   s_(i) is a respective amount of stress caused by the external        force F_(i); and    -   S_(i)(PDL) is a portion of the surface of the PDL 34 influenced        by a greater amount of stress than s_(i).

With reference to FIG. 9 , there is provided a stress nephogram 900having been generated by the processor 650, for the tooth 15 based onanalyzing the tooth 3D digital model 800, in accordance with certainnon-limiting embodiments of the present technology. Alternatively, theprocessor 650 may retrieve the stress nephogram 900 from a memory suchas the memory 670.

According to certain non-limiting embodiments of the present technology,the stress nephogram 900 is indicative of stress distribution within thePDL 34 under influence of various external forces defining the SCDF forthe tooth 15. More specifically, the stress nephogram 900 shows abehaviour of stress distributed within a respective portion of the PDL34 (indicated by the vertical axis in the stress nephogram 900) causedby a respective external force (indicated by the horizontal axis in thestress nephogram 900). Additionally or alternatively, the stressnephogram 900 may include data indicative of strain distribution withinthe PDL 34 under respective external forces.

Thus, in certain non-limiting embodiments of the present technology, thestress nephogram 900 may include an indication of (1) an admissiblestress distribution curve 902 indicating a distribution of admissiblestress, which does not cause permanent damage to the PDL 34, and thusmay cause the tooth 15 either to move or rest within the upper arch form20; (2) a dangerous stress distribution curve 904 indicating adistribution of dangerous stress, which, when applied to the PDL 34, maycause permanent damage thereof; and (3) an admissible straindistribution curve 906 indicating distribution of admissible strainwithin the PDL 34.

For example, according to the stress nephogram 900, a given force 908,F₁, applied to the tooth 15 may cause an admissible amount of stress to,approximately, 9% of a surface of the PDL 34; an admissible amountstrain to around 53% of the surface of the PDL 34, and no dangerousstress to the PDL 34. Thus, in this example, SCDF (F₁, s₁)=0.

Thus, according to certain non-limiting embodiments of the presenttechnology, the processor 650 may be configured to identify forcesrelating to the stress thresholds including: (i) a minimum force 910,F_(min), corresponding to the minimum stress threshold applied to thePDL 34 causing the tooth 15 to move, and (ii) a maximum force 912,F_(max), corresponding to an amount of stress beyond which permanentdamage to the PDL 34 may be caused. Thus, based on the stress nephogram900, the processor 650 may be configured to identify the following setsof forces:

-   -   1) the set of admissible forces applicable to the PDL 34 without        causing the permanent damage thereto:        F ^(adm): SCDF(F _(i) ,s ^(max))˜0, further including:  (2)    -   2) a set of forces causing the tooth 15 to rest:        F ^(rest): SCDF(F _(i) ,s ^(min))˜0, and  (3)    -   3) a set of drive forces causing the tooth 15 to move in a        respective direction associated with a each force therefrom:        F ^(drive): {SCDF(F _(i) ,s ^(max))˜0 SCDF(F _(i) ,s ^(min))>0⇒F        ^(drive)∈[F _(min) ^(drive) ,F _(max) ^(drive)].  (4)

Accordingly, as it may become apparent from the above, any force beyondthe set of admissible forces F^(adm) may cause the permanent damage tothe PDL 34 of the tooth 15.

Thus, the processor 650 may be configured to determine, based on arespective tooth 3D representation, a respective range of stressthresholds for each modelled movement (such as translation, rotation,controlled/uncontrolled tipping, or extrusion/intrusion, for example) ofeach one of the upper teeth 16 for further determining a respectivevalid force therefrom.

As mentioned earlier, the processor 650 may be configured to use the setof admissible forces F^(adm) to determine the respective valid force tobe applied to the tooth 15, in the course of the orthodontic treatment.

Referring now to FIG. 10 which depicts the induced stresses by the force40 applied in the PDL 34 of the tooth 15 with the stress thresholdsmarked thereon: minimum stress threshold, maximum stress threshold andoptimal stress threshold. The thresholds were derived for each toothusing finite element analysis. The area and magnitude of stressoccurring in the periodontal ligament was analyzed.

In the above manner, stress thresholds for a plurality of the upperteeth 16 may thus be determined, an example of which is illustrated inFIG. 11 .

Determining Transfer Forces

As noted hereinabove, force applied to the given tooth, such as thetooth 15 under the force 40 may cause application of transfer forces toat least some of the other teeth of the arch form 20.

According to certain non-limiting embodiments of the present technology,to determine the transfer forces, the processor 650 may be configured toapply a Displacement Response Force Distribution Function (DRFDF).According to certain non-limiting embodiments of the present technology,the DRFDF may be constructed based on a superposition property of theforces caused by a displacement of a given tooth 3D representationwithin the 3D digital model 700. Thus, for example, the additionalforces caused by the application of the force 40 applied to the 3Ddigital model 700 may be determined in accordance with the followingequation:F _(1 . . . n)=DRFDF₁ ×{right arrow over (d)} ₁,  (7)where F_(1 . . . n) is a vector of the transfer forces applied, in therespective treatment segment, to respective tooth 3D representationsinvolved in the orthodontic treatment in response to applying the force40 causing the first displacement of the tooth 15 {right arrow over(d)}₁; and

-   -   DRFDF₁ is a matrix of coefficients indicative of force magnitude        values of the transfer forces associated with the applying the        force 40.

According to certain non-limiting embodiments of the present technology,the DRFDF₁ may have dimensions of (6n×6), where n is a number of therespective teeth involved in the orthodontic treatment using the aligner10, and the dimension 6 corresponds to 6 DOF of each of the respectiveteeth, to which a respective one of the transfer forces propagates.

According to certain non-limiting embodiments of the present technology,the DRFDF₁ may be populated, for example, based on finite elementanalysis of the respective teeth 3D digital models, their associatedPDLs (such as the PDL 34 associated with the 3D digital model 700 of thetooth 15) with respective configurations of the aligner 10 appliedthereto.

Accordingly, in additional non-limiting embodiments of the presenttechnology, where the transfer forces are caused by respectivedisplacements of more than one tooth within the 3D digital model 700,the processor 650 may be configured to determine them in accordance withthe following equation:F _(1 . . . n)=Σ_(j)(DRFDF_(j) ×{right arrow over (d)} _(j)).  (8)

Thus, based on the applying the DRFDF, the processor 650 may beconfigured to determine the transfer forces F_(1 . . . n) includingtheir magnitudes and directions satisfying the following constraints asdescribed above in above in respect of Equations (2) to (4):

-   -   F_(j)∈F_(j) ^(adm)—an admissible stress constraint;    -   F_(j)∈F_(j) ^(drive)—forces used to cause a given tooth 3D        representation to move in directions associated therewith; and    -   F_(j)∈F_(j) ^(rest)—forces used to cause the given tooth 3D        representation to rest.

It should be expressly understood that the above list of constraintsapplied to the transfer forces F_(1 . . . n) is not exhaustive, and inadditional non-limiting embodiments of the present technology, mayfurther include constraints for a respective minimum stress threshold ofeach of the additional forces F_(1 . . . n)—for example, correspondingto the lower threshold (causing a given tooth to rest, F_(j) ^(rest)).Such constraints may be used to allow for proper reformation of a PDL ofa respective one of the upper teeth 16.

Thus, according to certain non-limiting embodiments of the presenttechnology, based on the DRFDF as defined by Equations (7) and (8), theprocessor 650 may be configured to determine each displacement of therespective tooth 3D representations within the 3D digital model 700, inthe treatment segment, caused by the transfer forces applied thereto inresponse to, at least, the applied force 40.

Tooth Trajectory and Segments

As mentioned above, the orthodontic treatment may be defined at least inpart by determining a trajectory segment of a given tooth with a giventreatment segment, such as the tooth 15 moving from the start positionS₁₅ to the target position T₁₅ (FIG. 4 ). The trajectory segment may beachieved over a plurality of treatment segments in which the tooth 15 ismoved by a determined distance through application of a determinedforce, such as a “valid force”, which takes into safety requirements ofat least one other tooth of the arch form 20.

Thus, in certain embodiments, the processor 650 may be configured todetermine at least one trajectory segment of the orthodontic treatment,the trajectory segment being indicative of a portion of the trajectoryof the given tooth from the start position to the target position. Incertain embodiments, the processor 650 is configured to determine allthe trajectory segments defining the trajectory from the start positionto the target position.

Referring to FIG. 12A, there is provided a schematic diagram of anexample schedule 1200 determined by the processor 650 of trajectories ofsome of the upper teeth 16, such as the tooth 15, the first adjacenttooth 13, and the second adjacent tooth 17, in accordance with certainnon-limiting embodiments of the present technology.

As it can be appreciated from the schedule 1200, each one of a firsttrajectory 1202, a second trajectory 1204, and a third trajectory 1206defining movements of the first adjacent tooth 13, the tooth 15, and thesecond adjacent tooth 17, respectively, is associated with at least twomoments in time: (1) an initial moment in time t_(j) ^(init) associatedwith a respective initial position of the tooth 15 (X₂ ^(init)), thefirst adjacent tooth 13 (X₁ ^(init)), and the second adjacent tooth 17(X₃ ^(init)) within the upper arch form 20, which, for example, may berepresentative of the current configuration of the these teeth asdepicted in FIG. 1 ; and (2) a final moment in time t_(f) ^(fin)associated with a respective target position of the tooth 15 (X₂^(fin)), the first adjacent tooth 13 (X₁ ^(fin)), and the secondadjacent tooth 17 (X₃ ^(fin)), such as that being indicative ofalignment of the tooth 15. FIG. 12A indicates that the tooth 15 maycontinue to be displaced after the tooth 13 and the tooth 15 havereached their target positions, the tooth 13 and the tooth 17 havingbeen moved to make space for the tooth 15.

According to certain embodiments of the present embodiment, presentmethods and systems can also determine the schedule of the differenttrajectory segments of the trajectory. The processor 650 may performthis, in certain embodiments, by optimizing preliminary trajectorysegments of the trajectory. The preliminary trajectory segments may bedetermined by the processor 650 in any applicable manner, such as bydividing the trajectory into trajectory segments of equal time, orapplying a predetermined time per trajectory segment to the trajectory.The preliminary trajectory segments may also have been determinedthrough a validation process performed by the processor 650, or anotherprocessor, such as collision detection.

FIG. 12B depicts the second trajectory 1204 of the tooth 15 in which thetrajectory 1204 has been sub-divided into three preliminary trajectorysegments, TS1, TS2 and TS3. t₂ ^(interim1) indicates the end time of thefirst trajectory segment TS1 and start of the second trajectory segmentTS2, and t₂ ^(interm2) indicates the end of the second trajectorysegment TS2 and the start of the third and final trajectory segment TS3.It will be appreciated that each trajectory segment may be associatedwith different movement distances and/or directions of the tooth 15, andhence different applied aligners 10 in each treatment segment. Each endand start time of the given tooth has an associated position of thetooth in the arch form 20.

An example of the optimized preliminary trajectory segments is alsodepicted in FIG. 12B as validated trajectory segments VTS1, VTS2, VTS3and VTS4. As can be seen, in certain embodiments, the validatedtrajectory segments may be modulated versions of the preliminarytrajectory segments, in terms of time (i.e. duration of each trajectorysegment) and/or number (i.e. number of trajectory segments within thetrajectory of the given tooth). In other embodiments, the validatedtrajectory segments may at least partially remain the same as thepreliminary trajectory segments. In the example of FIG. 12B, thevalidated trajectory segment VTS1 has a validated end time which isdifferent than the end time of the preliminary trajectory segment TS1.The validated end time will be the validated start time of the secondvalidated trajectory segment VTS2. It will be appreciated that eachvalidated end time of the given tooth will have an associated positionin the arch form 20 at the end of the validated trajectory segment.Similarly, each validated start time of the given tooth will have anassociated position in the arch form 20 at the start of the validatedtrajectory segment.

Accordingly, for determining at least one of the first trajectory 1202,the second trajectory 1204, and the third trajectory 1206 includingtheir respective validated trajectory segments, in certain non-limitingembodiments of the present technology, the processor 650 may beconfigured to determine or obtain, based on the 3D digital model 700 ora derivative thereof, the respective initial positions of at least oneof the tooth 15, the first adjacent tooth 13, and the second adjacenttooth 17 within the coordinate system 750 associated with the 3D digitalmodel 700. In other words, the processor 650 may be configured todetermine 6 degrees of freedom (DOF) of at least one of the tooth 15,the first adjacent tooth 13, and the second adjacent tooth 17 at a giveninitial moment in time t_(j) ^(init), to thereby identify the startposition (e.g. S₁₅, S₁₇) thereof within the upper arch form 20.

Further, according to certain non-limiting embodiments of the presenttechnology, the processor 650 may be configured to determine or obtain,based on the 3D digital model 700 or a derivative thereof, therespective target positions X_(j) ^(fin) of at least one of the tooth15, the first adjacent tooth 13, and the second adjacent tooth 17 withinthe coordinate system 750 associated with the 3D digital model 700. Inother words, the processor 650 may be configured to acquire 6 degrees offreedom (DOF) within the coordinate system 750 of the respective targetposition, of at least one of the tooth 15, the first adjacent tooth 13,and the second adjacent tooth 17, for example Tis in FIG. 4 . In somenon-limiting embodiments of the present technology, the respectivetarget position for each of the teeth may be provided by the clinician.In other non-limiting embodiments of the present technology, theprocessor 650 may be configured to determine the respective targetpositions based on averaged data associated with aligned teeth receivedfrom a group of patients.

According to certain embodiments of the present technology, theprocessor 650 may be configured to determine the validated trajectorysegments by optimizing, by the processor 650, a preliminary forceapplied to a given tooth of the tooth 3D digital model 800 at arespective initial moment in time t₂ ^(init).

The optimization, which will be described in further detail below, maybe based on the stress thresholds with the purpose of avoiding one ormore of: a damage to the tissues of the periodontium 30 of the tooth 15;a damage to the tissues of the periodontium 30 of the other teeth 16;and unintended tooth movement in the arch form 20.

Following the determination of the valid force to be applied to thetooth 15, the processor 650 may then be configured, in certainembodiments, to use the valid force to determine the validatedtrajectory segment by applying the validated force to the given tooth atthe start position of the preliminary trajectory segment. Thus,according to certain non-limiting embodiments of the present technology,by applying the valid force to the tooth 3D digital model 800 of thegiven tooth, a respective displacement of the given tooth may bemodelled to thereby determine the validated end position thereof. Thevalidated trajectory segment thus is considered to have the startposition and the validated end position.

The processor 650 may then determine the orthodontic treatment asincluding the validated trajectory segment. The validated trajectorysegment or the determined orthodontic treatment may be stored by theprocessor 650, such as in a memory of the computing system.

In certain embodiments, the processor 650 may also be configured todetermine other validated trajectory segments of the given trajectory,by assuming for example that the validated end position of a priortrajectory segment is equivalent to the validated start position of anext trajectory segment. In this manner, the processor 650 may beconfigured to determine all the validated trajectory segments of a giventrajectory for a given tooth. The processor 650 may also be configuredto repeat this process for other teeth 16 of the arch form 20.

According to certain embodiments of the present technology, theprocessor 650 is configured to apply one or more validation processes tothe one or more validated trajectory segments or to the one or morepreliminary trajectory segments. One example of a validation process iscollision detection in which it is determined whether the relativemovement of the teeth within a treatment segment may give rise tocollisions between the teeth. Any suitable method can be used by theprocessor 650 for collision detection such as that described in aco-owned U.S. Pat. No. 10,993,782-B1, entitled “SYSTEMS AND METHODS FORDETERMINING A TOOTH TRAJECTORY”, issued on May 4, 2021; the content ofwhich is hereby incorporated by reference in its entirety; and asdescribed in a co-owned U.S. Pat. No. 10,695,146-B1 entitled “SYSTEMSAND METHODS FOR DETERMINING ORTHODONTIC TREATMENTS”, issued on Jun. 30,2020; the content of which is hereby incorporated by reference in itsentirety.

Once the validated trajectory segments of a given treatment segment areobtained, the processor 650 may be configured to determine theorthodontic appliance to apply to the teeth in that given treatmentsegment based on the determined valid forces to be applied to the teeth.

In certain embodiments, the processor 650 is configured to cause amanufacture of the so determined orthodontic appliance, such as thealigner 10, by sending instructions to a manufacturing system such asthe manufacturing system 540.

Optimization

Turning now to the optimization applied by the processor 650 todetermine the valid force and hence the validated trajectory segment.The optimization will be described with reference to determining thevalidated trajectory segment VTS1 for the tooth 15 in the trajectory1204 (FIG. 12B). As noted above, embodiments of the present technologytake into consideration the preliminary force applied to the tooth 3Ddigital model 800 of the tooth 15 at the initial moment in time t₂^(init) to displace the tooth 15 to an end position of the preliminarytrajectory segment, such as a position associated with t₂ ^(termin1).

In certain embodiments, the preliminary force may be based on anarbitrary value that is selected or obtained by the processor 650. Thearbitrary value may be a predetermined force value. In such a case, thepreliminary force may be determined as the force required to move thegiven tooth along the predetermined tooth movement distance in a givensegment treatment time or for the predetermined segment treatment time.

It should be noted that as the preliminary force is arbitrary it mayviolate a safety requirement. This may be confounded by the preliminarytrajectory segment in certain embodiments also being somewhat arbitrary.For example, the preliminary force when applied to the tooth 15 maycause one or more of: a damage to the tissues of the periodontium 30 ofthe tooth 15; a damage to the tissues of the periodontium 30 of theother teeth 16; and unintended tooth movement in the arch form 20. Forexample, applying the preliminary force to the tooth 15 in order to moveonly the tooth 15 may cause movement of the tooth 13 or the tooth 17 (asdepicted in FIG. 4 , for example).

The optimization is, in certain embodiments, based on the transferforces related to the preliminary force applied to the tooth 15. Asnoted above, transfer forces are related to stresses induced in PDLs orother tissues associated with the other teeth of the arch form (i.e.other than the tooth to which the force was applied). Stress thresholds,as mentioned above, may be defined in certain embodiments of the presenttechnology as being the minimum stress threshold below which the giventooth does not move, the maximum stress threshold above which damage inincurred, and the optimal stress threshold in which movement of thetooth is induced without damage.

The processor 650 is thus configured to determine an induced stress ortransfer force associated with at least one other of the upper teeth 16of the upper arch form 20, such as in the manner described herein, andresponsive to the determined induced stress, determine whether tomodulate the preliminary force. If modulation is required, the processormay be configured to modulate the preliminary force to a desirablelevel.

The determination of whether and how to modulate the preliminary forcedepends on for example one or both of: avoiding damage to the tissues ofthe periodontium 30 of the tooth 15; avoiding damage to the tissues ofthe periodontium 30 of the other teeth 16 of the upper arch form 20;avoiding and unintended tooth movement of the other teeth 16 in theupper arch form 20; and not meeting a desired movement of the otherteeth 16 in the upper arch form 20. If the induced stress is found notto meet a threshold level, the preliminary force may be modulated untila desired stress level is met.

In one example, in order to avoid or minimize damage to the tissues ofthe periodontium 30 of the other teeth 16 of the upper arch form 20, theprocessor 650 may determine the valid force as being lower than thepreliminary force if the determined induced stress is above the maximumstress threshold for the given other tooth. For example if the inducedstress of the tooth 13 or the tooth 17 is above the maximum stressthreshold, the processor 650 may be configured to lower the preliminaryforce.

In another example, in order to avoid or minimize unintended toothmovement of the other teeth 16 in the upper arch form 20, the processor650 may determine the valid force as being lower than the preliminaryforce if the determined induced stress is above the minimum stressthreshold for the given other tooth (but below the maximum stressthreshold). For example if the induced stress of the tooth 13 or thetooth 17 is above the minimum stress threshold but below the maximumstress threshold, the processor 650 may be configured to determine thevalid force as being lower than the preliminary force.

In yet another example, in order to obtain a desired tooth movement ofsome of the other teeth 16 in the upper arch form 20, the processor 650may be configured to determine the valid force as being higher than thepreliminary force if the determined induced stress is below the minimumstress threshold for the given other tooth. For example, if the inducedstress of the tooth 13 or the tooth 17 is below the minimum stressthreshold despite a desired movement of the tooth 13 or the tooth 17,the processor 650 may be configured to increase the preliminary force.

In yet another example, in order to avoid or minimize damage to thetissues of the periodontium 30 of the tooth 15 of the upper arch form20, the processor 650 may be configured to determine the valid force asbeing less than the preliminary force if the determined induced stressis above the maximum stress threshold for the tooth 15.

In these examples in which the preliminary force is modulated until adesired outcome is achieved (such as a desirable induced stress level inthe tooth 15 or the other teeth 16), the modulated preliminary force isdetermined to be the valid force.

The processor 650 can then apply the valid force to the start positionof the preliminary trajectory segment to obtain the validated endposition and hence define the validated trajectory segment.

The processor 650 may be configured to then repeat the above but usingthe validated end position as the start position of a next preliminarytrajectory segment. This can be repeated until all the validatedtrajectory segments of the trajectory are determined.

In certain embodiments, the processor 650 may be configured to repeatthis process based on determined induced stresses associated withanother tooth. In certain embodiments, the processor 650 is configuredto determine induced stresses associated with all of the upper teeth 16of the upper arch form 20.

In certain embodiments, if the induced stress associated with the atleast other tooth of the upper arch form 20 is determined to be abovethe minimum stress threshold of that tooth and hence cause that tooth tomove, if the movement of that tooth is undesired (according to an inputreceived by the processor 650 for example), the processor 650 maydetermine that a counter force should be applied to that tooth toprevent or minimize its movement. In this respect, the processor 650 maycalculate the counter force that this required to be applied to theother tooth to avoid its movement.

Method

Given the architecture and the examples provided hereinabove, it ispossible to execute a method for determining a tooth trajectory for agiven one of patient's teeth (such as the tooth 15 of the upper teeth16) defining movements thereof during an orthodontic treatment. Withreference to FIG. 13 , there is depicted a flowchart of one aspect of amethod 1300, according to certain non-limiting embodiments of thepresent technology. The method 1300 can be executed by a processor of acomputing environment, such as the processor 650 of the computingenvironment 640.

Step 1302: Acquiring 3D Digital Model of an Arch Form of the Subject

The method 1300 commences at step 1302 with the processor 650 acquiringa 3D digital model of an arch form of the subject, such as the 3Ddigital model 700 of the arch form 20. The 3D digital model of the archform may include representations of a plurality of the subject's teethincluding a 3D digital model of a given tooth associated with thesubject. For example, in certain non-limiting embodiments of the presenttechnology, using the imaging device 530, the processor 650 may beconfigured to generate the 3D digital model 700 representative of theupper arch form 20 of the subject, as described above with reference toFIG. 7 .

Further, according to some non-limiting embodiments of the presenttechnology, the processor 650 may be configured to generate, based onthe 3D digital model 700, respective tooth 3D digital models, forexample, of the upper teeth 16—such as the tooth 3D digital model 800 ofthe tooth 15 (FIG. 8 ). The processor 650 may be further configured touse the tooth 3D digital model 800 or the 3D digital model 700 fordetermining a trajectory for the tooth 15 in the course of theorthodontic treatment—such as the second trajectory 1204, as describedabove with reference to FIG. 12A.

The method 1300 hence advances to step 1304.

Step 1304: Identifying an Initial Position of the Given Tooth

At step 1304, the processor 650 may be configured to identify an initialposition of the tooth 15 within the upper arch form 20. In certainembodiments, the processor 650 may use the 3D digital model 700 or thetooth 3D digital model 800. According to certain non-limitingembodiments of the present technology, the processor 650 may beconfigured to determine 6 DOF of the tooth 3D digital model 800 at theinitial moment in time, <X₂ ^(init), t₂ ^(init)>, as described abovewith reference to FIGS. 12A and 12B.

Step 1306: Acquiring an Indication of a Target Position of the GivenTooth

At step 1306, the processor may be configured to acquire a targetposition of the given tooth, such as from the tooth 3D digital model800. The target position may be defined as six DOF. For example, thetarget position for the tooth 15 is indicated as X₂ ^(fin). According tocertain non-limiting embodiments of the present technology, the targetposition X₂ ^(fin) may be associated with the aligned position of thetooth 15 within the upper arch form 20.

In some non-limiting embodiments of the present technology, the targetposition for the tooth 15 may be provided by the clinician. In othernon-limiting embodiments of the present technology, the processor 650may be configured to determine the target position based on averageddata associated with aligned teeth received from a group of subjects.

The method 1300 thus proceeds to step 1308.

Step 1308: Obtaining a Preliminary Trajectory of the Given Tooth fromthe Initial Tooth Position to the Target Tooth Position, The PreliminaryTrajectory Comprising a Plurality of Preliminary Trajectory Segments

At step 1308, the processor 650 may be configured to obtain apreliminary trajectory of the tooth 15 from the initial tooth positionto the target tooth position. The preliminary trajectory may be thesecond trajectory 1204 of the tooth 15. The preliminary trajectory maycomprise a plurality of preliminary trajectory segments, such as thefirst trajectory segment TS1, the second trajectory segment TS2 and thethird trajectory segment TS3. The preliminary trajectory segments may bedetermined by the processor 650 in any applicable manner, such as bydividing the trajectory into trajectory segments of equal time, orapplying a predetermined time per trajectory segment to the trajectory.The preliminary trajectory segments may also have been determinedthrough a validation process performed by the processor 650, or anotherprocessor, such as collision detection.

The method 1300 thus proceeds to step 1310.

Step 1310: Determining the Tooth Trajectory for the Given Tooth from thePreliminary Trajectory by Executing an Optimization Algorithm on a FirstPreliminary Trajectory Segment of the Plurality of PreliminaryTrajectory Segments

At step 1310, according to certain non-limiting embodiments of thepresent technology, the processor 650 may be configured to determine thetooth trajectory for the given tooth from the preliminary trajectory byexecuting an optimization algorithm on a first preliminary trajectorysegment of the plurality of preliminary trajectory segments. For thegiven tooth 15, the tooth trajectory may be one or more of the validatedtrajectory segments VTS1, VTS2 and VTS3.

In certain embodiments, the optimization algorithm comprises applying afirst preliminary force to the 3D digital model of the given tooth todisplace the given tooth from a start position to an end position of thefirst preliminary trajectory segment within a predetermined timeinterval. For the given tooth 15, the start position is X₂ ^(init) andthe end position is t₂ ^(interm1).

Next, the processor 650 may determine a first induced stress associatedwith at least one other of the plurality of subject's teeth, such as thetooth 13 and the tooth 17. The first induced stress may be determined bythe processor 650 according to method described above with reference to“transfer forces”.

In response to a determination that the first induced stress does notmeet a threshold level, the processor 650 may modulate the firstpreliminary force such that the first induced stress is modulated to adesirable level, thereby determining a first valid force to be appliedto the given tooth. The threshold level may have been determined orobtained by the processor 650 according to methods described above withreference to stress threshold levels and FIGS. 10 and 11 .

The processor 650 can then apply the first valid force to the giventooth, such as the tooth 15, at the start position X₂ ^(init) of thefirst preliminary trajectory segment, such as TS1, to determine avalidated end position, such as t₂ ^(Vinterim1), of the firstpreliminary trajectory segment, TS1, thereby defining a first validatedtrajectory segment, such as VTS1 (FIG. 12B). The processor 650 may thusdetermine the tooth trajectory of the given tooth as including the firstvalidated trajectory segment having the start position and the validatedend position.

The method 1300 thus proceeds to step 1312.

Step 1312: Storing Data Indicative of the Determined Tooth Trajectory orthe Orthodontic Treatment in a Memory Communicatively Coupled to theProcessor

At step 1312, according to certain non-limiting embodiments of thepresent technology, the processor 650 may be configured to store, forexample, in the solid-state drive 660, data indicative of the determinedtooth trajectory, such as each one of the plurality of segmentsassociated with the second trajectory 1204 for further planning theorthodontic treatment.

The method thus proceeds to step 1314.

Step 1314: Using the Tooth Trajectory for the Given Tooth for Planningthe Orthodontic Treatment of the Subject

According to certain non-limiting embodiments of the present technology,the processor 650, may be configured to used the determined toothtrajectory to plan the orthodontic treatment. For example, the toothtrajectory of the other teeth may be determined and the aligner 10designed and generated for imparting the orthodontic treatment.

According to certain non-limiting embodiments of the present technology,for planning the orthodontic treatment, the processor 650 may beconfigured to represent the so determine trajectories (such as the firsttrajectory 1202, the second trajectory 1204, and the third trajectory1206) in a form of a schedule, such as the planned schedule 1200depicted in FIG. 12A.

In some non-limiting embodiments of the present technology, each of thepredetermined treatment segments may be associated with using arespective configuration of the aligner 10 configured to apply, during arespective one of the plurality of predetermined treatment segments.

Thus, certain embodiments of the method 1300 allow developing moreefficient and safer orthodontic treatments. More specifically, applyingthe method 1300 for planning the orthodontic treatment may allow (1)avoiding application of forces that may cause damage to tissues ofperiodontium associated with respective ones of the subject's teeth; (2)avoiding application of forces that may cause damage to tissues ofperiodontium associated with respective other ones of the subject'steeth; while (3) maximizing displacements of each of the respective onesof the subject's teeth, thereby reducing a number of associated alignersto be used in the course of the planned orthodontic treatment.

The method 1300 hence terminates.

With reference to FIG. 14 , there is depicted a flowchart of anotheraspect of a method 1400, according to certain non-limiting embodimentsof the present technology. The method 1400 can be executed by aprocessor of a computing environment, such as the processor 650 of thecomputing environment 640.

Step 1402: Acquiring 3D Digital Model of an Arch Form

The method 1400 commences at step 1402 with the processor 650 acquiringa 3D digital model of an arch form of the subject, the 3D digital modelincluding representations of a plurality of the subject's teeth, such asthe upper teeth 16, including for example a 3D digital model of a giventooth. For example, in certain non-limiting embodiments of the presenttechnology, using data from the imaging device 530, the processor 650may be configured to generate the 3D digital model 700 representative ofthe upper arch form 20 of the subject, as described above with referenceto FIG. 7 , and including a representation of the tooth 15.

Further, according to some non-limiting embodiments of the presenttechnology, the processor 650 may be configured to generate, based onthe 3D digital model 700, respective tooth 3D digital models, forexample, of the upper teeth 16—such as the tooth 3D digital model 800 ofthe tooth 15 (FIG. 8 ). The processor 650 may be further configured touse the tooth 3D digital model 800 for determining a trajectory for thetooth 15 in the course of the orthodontic treatment—such as the secondtrajectory 1204, as described above with reference to FIG. 12A.

The method 1400 hence advances to step 1404.

Step 1404: Identifying an Initial Position of the Given Tooth

At step 1404, the processor 650 may be configured to identify an initialposition of the tooth 15 within the upper arch form 20. To that end,according to certain non-limiting embodiments of the present technology,the processor 650 may be configured to determine the initial positionbased on the 3D digital model 700 or the tooth 3D digital model 800. Incertain embodiments, the initial position may be defined as six DOF ofthe tooth 15 at the initial moment in time, <X₂ ^(init), t₂ ^(init)>,such as described above with reference to FIGS. 12A and 12B.

The method 1400 thus proceeds to step 1406.

Step 1406: Acquiring an Indication of a Target Position of the GivenTooth

At step 1406, the processor 650 may be configured to acquire a targetposition of the tooth 15, which may be defined as a six DOF of the toothin the 3D digital model 700 or the tooth 3D digital model 800 (such asX₂ ^(fin)). According to certain non-limiting embodiments of the presenttechnology, the target position X₂ ^(fin) may be associated with thealigned position of the tooth 15 within the upper arch form 20.

In some non-limiting embodiments of the present technology, the targetposition for the tooth 15 may be provided by the clinician. In othernon-limiting embodiments of the present technology, the processor 650may be configured to determine the target position based on averageddata associated with aligned teeth received from a group of subjects.

The method 1400 thus proceeds to step 1408.

Step 1408: Obtaining a Trajectory of the Given Tooth from the InitialTooth Position to the Target Tooth Position, The Trajectory Comprising aPlurality of Trajectory Segments

At step 1408, the processor 650 may be configured to obtain a trajectoryof the tooth 15 from the initial tooth position to the target toothposition. The trajectory may be the second trajectory 1204 of the tooth15. The trajectory may comprise a plurality of trajectory segments, suchas the first trajectory segment TS1, the second trajectory segment TS2and the third trajectory segment TS3. The trajectory segments may bedetermined by the processor 650 in any applicable manner, such as bydividing the trajectory into trajectory segments of equal time, orapplying a predetermined time per trajectory segment to the trajectory.The preliminary trajectory segments may also have been determinedthrough a validation process performed by the processor 650, or anotherprocessor, such as collision detection.

The method 1400 thus proceeds to step 1410.

Step 1410: For a Given Segment of the Plurality of Trajectory Segments,Applying a Force to the 3D Digital Model of the Given Tooth to Displacethe Given Tooth from a Start Position to an End Position of theTrajectory Segment within a Predetermined Time Interval and Determiningan Induced Stress Associated with at Least One Other of the Plurality ofSubject's Teeth

At step 1410, according to certain non-limiting embodiments of thepresent technology, the processor 650 may be configured to simulate inthe 3D digital model, a force being applied to the given tooth, such asthe tooth 15, to move it from a start position to an end position of thetrajectory segment. For the given tooth 15, the tooth trajectory segmentmay be one or more of the validated trajectory segments VTS1, VTS2 andVTS3.

In certain embodiments, the processor 650 may be configured to determinethe force to be applied to move the given tooth from the start positionto the end position in the tooth trajectory segment. The determinationmay be based on the movement occurring within a predetermined timeinterval. For the given tooth 15, the start position may be X₂ ^(init)and the end position may be t₂ ^(interm1).

Next, the processor 650 may determine an induced stress associated withat least one other of the plurality of subject's teeth, such as thetooth 13 and/or the tooth 17. The induced stress may be determined bythe processor 650 according to method described above with reference to“transfer forces”. The processor 650 may be configured to determine theinduced stress associated with all the upper teeth 16 as a result of theforce 40 applied to the given tooth 15.

The method 1400 thus proceeds to step 1412.

Step 1412: In Response to A Determination that the Induced Stress isAbove a Threshold Level, Determining a Counter Force to be Applied tothe at Least One Other of the Plurality of Subject's Teeth in Order toCounter the Induced Stress to Avoid Movement of the at Least One Otherof the Plurality of Subject's Teeth

In response to a determination that the induced stress is above athreshold level, the processor 650 may determine a counter force to beapplied to the at least one other of the teeth 16.

The threshold level may be based on an induced movement of the at leastone other of the teeth 16 from the induced stress. In some cases, anyinduced movement of the at least one other of the teeth 16 may not bedesirable or wanted, the threshold level being set relatively low. Inother cases, some induced movement of the at least one other of theteeth 16 may be tolerated within the planned orthodontic treatment, thethreshold level being set relatively higher.

The threshold level may also be based on a potential damage to the PDLof the at least one other of the teeth 16 from the induced stress.

The threshold level may have been determined or obtained by theprocessor 650 according to methods described above with reference tostress threshold levels and FIGS. 10 and 11 .

The processor 650 may be configured to determine the counter force basedon a desired outcome related to the at least one other of the teeth 16.For example, the counter force may be determined based on fullycountering the induced movement of the at least one other of the teeth16 from the induced stress. In other examples, the counter force may bedetermined based on partially countering the induced movement of the atleast one other of the teeth 16 from the induced stress. In yet otherexamples, the counter force may be determined based on directing theinduced movement of the at least one other of the teeth 16 from theinduced stress, in terms of a direction of movement.

The processor 650 may thus be configured to determine the orthodontictreatment as including the force applied to the given tooth and thecounter force applied to the at least one other of the plurality ofsubject's teeth.

The method thus proceeds to step 1414.

Step 1414: Storing Data Indicative of the Determined OrthodonticTreatment in a Memory Communicatively Coupled to the Processor

At step 1414, according to certain non-limiting embodiments of thepresent technology, the processor 650 may be configured to store, forexample, in the solid-state drive 660, data indicative of the determinedorthodontic treatment relating to the treatment segment.

According to certain non-limiting embodiments of the present technology,the processor 650, may be configured to use the determined force and thedetermined counter force to design and manufacture an orthodonticappliance, such as the aligner 10, to apply the determined force and thedetermined counter force in the treatment segment.

According to certain non-limiting embodiments of the present technology,the processor 650 may be configured to repeat at least some of theabovementioned steps for determining induced stresses for other teeth ofthe same arch form.

According to certain non-limiting embodiments of the present technology,the processor 650 may be configured to repeat at least some of theabovementioned steps for other treatment segments of the trajectory.

According to certain non-limiting embodiments of the present technology,the processor 650 may be configured to repeat at least some of theabovementioned steps for other trajectories of other teeth of thesubject.

The processor 650 may be configured to represent the so determinetrajectories (such as the first trajectory 1202, the second trajectory1204, and the third trajectory 1206) in a form of a schedule, such asthe planned schedule 1200 depicted in FIG. 12A.

In some non-limiting embodiments of the present technology, each of thepredetermined treatment segments may be associated with using arespective configuration of the aligner 10 configured to apply, during arespective one of the plurality of predetermined treatment segments.

Thus, certain embodiments of the method 1400 allow developing moreefficient and safer orthodontic treatments. More specifically, applyingthe method 1400 for planning the orthodontic treatment may take intoaccount induced movements of teeth from induced stresses and avoidunwanted movements.

The method 1400 hence terminates.

It should be expressly understood that not all technical effectsmentioned herein need to be enjoyed in each and every embodiment of thepresent technology.

Modifications and improvements to the above-described implementations ofthe present technology may become apparent to those skilled in the art.The foregoing description is intended to be exemplary rather thanlimiting. The scope of the present technology is therefore intended tobe limited solely by the scope of the appended claims.

The invention claimed is:
 1. A method for determining an orthodontictreatment for a tooth of a subject, the method being executable by aprocessor of an electronic device, the method comprising: acquiring a 3Ddigital model of an arch form of the subject, the 3D digital model ofthe arch form including representations of a plurality of the subject'steeth including: a 3D digital model of the given tooth; an initial toothposition of the given tooth; an indication of a target tooth positionfor the given tooth; and a trajectory of the given tooth defining a paththereof from the initial tooth position to the target tooth position,the trajectory comprising a plurality of trajectory segments, a giventrajectory segment being associated with a force value of a force to beapplied to the given tooth to cause a movement thereof along the giventrajectory segment; determining whether application of the force to the3D digital model of the given tooth causes an induced stress associatedwith at least one other of the plurality of the subject's teeth; inresponse to a determination that the induced stress is outside of apredetermined threshold level, whereby the induced stress causes amovement of the at least one other of the plurality of the subject'steeth, determining a counter force to be applied thereto so as tomodulate the movement thereof; and storing data indicative of the giventrajectory segment including data of the force to be applied to thegiven tooth and that of the determined counter force to be applied tothe at least one other of the plurality of the subject's teeth in amemory communicatively coupled to the processor.
 2. The method of claim1, wherein the predetermined threshold level comprises a minimum stressthreshold above which the at least one other of the plurality of thesubject's teeth is caused to move.
 3. The method of claim 2, wherein thecounter force is determined so as to reduce a movement of the at leastone other of the plurality of the subject's teeth.
 4. The method ofclaim 2, wherein the counter force is determined so as to direct amovement of the at least one other of the plurality of the subject'steeth.
 5. The method of claim 1, further comprising determining theforce to be applied to the 3D digital model of the given tooth, thedetermining comprising: obtaining a minimum stress threshold for thegiven tooth, the minimum stress threshold comprising a minimum amount ofstress required to cause the given tooth to move; obtaining a maximumstress threshold for the given tooth, the maximum stress thresholdcomprising a minimum amount of stress which would cause permanent damageto soft tissues around the given tooth; and determining the force asthat which induces a stress in the given tooth between the minimumstress threshold and the maximum stress threshold.
 6. The method ofclaim 5, further comprising determining one or both of the minimumstress threshold and the maximum stress threshold of the given toothusing a finite element analysis (FEA) method.
 7. The method of claim 1,further comprising using the force and the determined counter force fordetermining the orthodontic treatment for the subject.
 8. The method ofclaim 1, wherein the predetermined threshold level is determined basedon a minimum stress threshold of a respective one of the other of theplurality of the subject's teeth, and a maximum stress threshold of therespective one of the other of the plurality of the subject's teeth, theminimum stress threshold comprising a minimum amount of stress requiredto cause the given respective tooth to move, and the maximum stressthreshold comprising a minimum amount of stress which would causepermanent damage to soft tissues around the given respective tooth. 9.The method of claim 8, further comprising determining one or both of theminimum stress threshold and the maximum stress threshold of the givenrespective tooth using a finite element method on the given respectivetooth.
 10. The method of claim 1, further comprising displaying, on adisplay of the electronic device, the determined orthodontic treatmentof the trajectory segment.
 11. The method of claim 1, further comprisingcausing a manufacture of an orthodontic aligner according to thedetermined orthodontic treatment.
 12. A system for determining anorthodontic treatment for a tooth of a subject, the system comprising aprocessor of an electronic device, the processor being configured toexecute a method comprising: acquiring a 3D digital model of an archform of the subject, the 3D digital model of the arch form includingrepresentations of a plurality of the subject's teeth including: a 3Ddigital model of the given tooth; an initial tooth position of the giventooth; an indication of a target tooth position for the given tooth; anda trajectory of the given tooth defining a path thereof from the initialtooth position to the target tooth position, the trajectory comprising aplurality of trajectory segments, a given trajectory segment beingassociated with a force value of a force to be applied to the giventooth to cause a movement thereof along the given trajectory segment;determining whether application of the force to the 3D digital model ofthe given tooth causes an induced stress associated with at least oneother of the plurality of the subject's teeth; in response to adetermination that the induced stress is outside of a predeterminedthreshold level, whereby the induced stress causes a movement of the atleast one other of the plurality of the subject's teeth, determining acounter force to be applied thereto so as to modulate the movementthereof; and storing data indicative of the given trajectory segmentincluding data of the force to be applied to the given tooth and that ofthe determined counter force to be applied to the at least one other ofthe plurality of the subject's teeth in a memory communicatively coupledto the processor.
 13. A method for determining a tooth trajectory inorthodontic treatment for a tooth of a subject, the method beingexecutable by a processor of an electronic device, the methodcomprising: acquiring a 3D digital model of an arch form of the subject,the 3D digital model of the arch form including representations of aplurality of the subject's teeth including: a 3D digital model of thegiven tooth; an initial tooth position of the given tooth; an indicationof a target tooth position for the given tooth; and a preliminarytrajectory of the given tooth from the initial tooth position to thetarget tooth position, the preliminary trajectory comprising a pluralityof preliminary trajectory segments, the plurality of preliminarytrajectory segments having been determined so as to minimize a number ofsegments required to move the given tooth from the initial toothposition to the target tooth position; determining the tooth trajectoryfor the given tooth from the preliminary trajectory by applying theretoan optimization algorithm, such that: a given validated trajectorysegment of the tooth trajectory is associated to a respective validforce to be applied to the given tooth to cause a movement thereof alongthe given validated trajectory segment, the respective valid force notcausing stress to at least one other of the plurality of the subject'steeth greater than a desirable level of stress; using the determinedtooth trajectory of the given tooth as part of the orthodontic treatmentof the subject; and storing data indicative of the determined toothtrajectory or the orthodontic treatment in a memory communicativelycoupled to the processor.
 14. The method of claim 13, wherein thedesirable level of stress has been determined based on a minimum stressthreshold of a respective one of the other of the plurality of thesubject's teeth, and a maximum stress threshold of the respective one ofthe other of the plurality of the subject's teeth, the minimum stressthreshold comprising a minimum amount of stress required to cause thegiven respective tooth to move, and the maximum stress thresholdcomprising a minimum amount of stress which would cause permanent damageto soft tissues around the given respective tooth.
 15. The method ofclaim 13, wherein applying the optimization algorithm to a respectivepreliminary trajectory segment of the preliminary trajectory to generatethe given validated trajectory segment of the tooth trajectorycomprises: applying a given preliminary force to the 3D digital model ofthe given tooth to displace the given tooth from a start position to anend position of the respective preliminary trajectory segment within apredetermined time interval; determining an induced stress associatedwith at least one other of the plurality of the subject's teeth; inresponse to a determination that the induced stress does not meet athreshold level, modulating the given preliminary force such that theinduced stress is modulated to the desirable level of stress, therebydetermining the respective valid force to be applied to the given tooth;and applying the respective valid force to the given tooth at the startposition of the respective preliminary trajectory segment to determine avalidated end position of the respective preliminary trajectory segment,thereby defining the given validated trajectory segment.
 16. The methodof claim 15, further comprising determining the given preliminary forceto be applied to the 3D model of the given tooth, the determiningcomprising: obtaining a minimum stress threshold for the given tooth,the minimum stress threshold comprising a minimum amount of stressrequired to cause the given tooth to move; obtaining a maximum stressthreshold for the given tooth, the maximum stress threshold comprising aminimum amount of stress which would cause permanent damage to softtissues around the given tooth; and determining the given preliminaryforce as being a force which would induce a stress in the given toothbetween the minimum stress threshold and the maximum stress threshold.17. The method of claim 13, further comprising displaying, on a displayof the electronic device, the determined orthodontic treatment of thetrajectory segment.